tests: add targets for building libvirt inside Docker containers

The Travis CI system uses Docker containers for its build environment.
These are pre-built and hosted under quay.io/libvirt so that developers
can use them for reproducing problems locally.

Getting the right Docker command syntax to use them, however, is not
entirely easy. This patch addresses that usability issue by introducing
some make targets. To run a simple build (aka 'make all') using the
Fedora 28 container:

   make ci-build@fedora-28

To also run unit tests

   make ci-check@fedora-28

This is just syntax sugar for calling the previous command with a
custom make target

   make ci-build@fedora-28 CI_MAKE_ARGS="check"

To do a purely interactive build it is possible to request a shell

   make ci-shell@fedora-28

To do a MinGW build, it is currently possible to use the fedora-rawhide
image and request a different configure script

   make ci-build@fedora-rawhide CI_CONFIGURE=mingw32-configure

It is also possible to do cross compiled builds via the Debian containers

   make ci-build@debian-9-cross-s390x

In all cases the GIT source tree is cloned locally into a 'ci-tree/src'
sub-directory which is then exposed to the container at '/src'. It is
setup to use a separate build directory so the build takes place in a
subdir '/src/build'. A source tree build can be requested instead
by passing an empty string CI_VPATH= arg to make.

The make rules are kept in a standalone file that is included into the
main Makefile.am, so that it is possible to run them without having to
invoke autotools first.

It is neccessary to disable the gnulib submodule commit check because
this fails due to the way we have manually cloned submodule repos as
primary git repos with their own .git directory, instead of letting
git treat them as submodules in the top level .git directory.

  make[1]: Entering directory '/src/build'
  fatal: Not a valid object name origin
  fatal: run_command returned non-zero status for .gnulib
  .
  maint.mk: found non-public submodule commit
  make: *** [/src/maint.mk:1448: public-submodule-commit] Error 1

Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

.gitignore

@@ -44,6 +44,7 @@
 /autom4te.cache
 /build-aux/*
 /build/
+/ci-tree/
 /confdefs.h
 /config.cache
 /config.guess

Makefile.am

@@ -106,3 +106,5 @@ gen-AUTHORS:
 	  mv -f $(distdir)/AUTHORS-tmp $(distdir)/AUTHORS && \
 	  rm -f all.list maint.list contrib.list; \
 	fi
+
+include Makefile.ci

Makefile.ci

@@ -0,0 +1,220 @@
+# -*- makefile -*-
+# vim: filetype=make
+
+# Figure out name and path to this file. This isn't
+# portable but we only care for modern GNU make
+CI_MAKEFILE = $(abspath $(firstword $(MAKEFILE_LIST)))
+
+# The directory holding content on the host that we will
+# expose to the container.
+CI_SCRATCHDIR = $(shell pwd)/ci-tree
+
+# The root directory of the libvirt.git checkout
+CI_GIT_ROOT = $(shell git rev-parse --show-toplevel)
+
+# The directory holding the clone of the git repo that
+# we will expose to the container
+CI_HOST_SRCDIR = $(CI_SCRATCHDIR)/src
+
+# The directory holding the source inside the
+# container. ie where we told Docker to expose
+# the $(CI_HOST_SRCDIR) directory from the host
+CI_CONT_SRCDIR = /src
+
+# Relative directory to perform the build in. This
+# defaults to using a separate build dir, but can be
+# set to empty string for an in-source tree build.
+CI_VPATH = build
+
+# The directory holding the build output inside the
+# container.
+CI_CONT_BUILDDIR = $(CI_CONT_SRCDIR)/$(CI_VPATH)
+
+# Can be overridden with mingw{32,64}-configure if desired
+CI_CONFIGURE = $(CI_CONT_SRCDIR)/configure
+
+# Default to using all possible CPUs
+CI_SMP = $(shell getconf _NPROCESSORS_ONLN)
+
+# Any extra arguments to pass to make
+CI_MAKE_ARGS =
+
+# Any extra arguments to pass to configure
+CI_CONFIGURE_ARGS =
+
+# Avoid pulling submodules over the network by locally
+# cloning them
+CI_SUBMODULES = .gnulib src/keycodemapdb
+
+# Location of the Docker images we're going to pull
+# Can be useful to overridde to use a locally built
+# image instead
+CI_IMAGE_PREFIX = quay.io/libvirt/buildenv-
+
+# Docker defaults to pulling the ':latest' tag but
+# if the Docker repo above uses different conventions
+# this can override it
+CI_IMAGE_TAG = :master
+
+# We delete the virtual root after completion, set
+# to 0 if you need to keep it around for debugging
+CI_CLEAN = 1
+
+# We'll always freshly clone the virtual root each
+# time in case it was not cleaned up before. Set
+# to 1 if you want to try restarting a previously
+# preserved env
+CI_REUSE = 0
+
+# We need the container process to run with current host IDs
+# so that it can access the passed in build directory
+CI_UID = $(shell id -u)
+CI_GID = $(shell id -g)
+
+# Docker doesn't require the IDs you run as to exist in
+# the container's /etc/passwd & /etc/group files, but
+# if they do not, then libvirt's  'make check' will fail
+# many tests.
+#
+# We do not directly mount /etc/{passwd,group} as Docker
+# is liable to mess with SELinux labelling which will
+# then prevent the host accessing them. Copying them
+# first is safer.
+CI_PWDB_MOUNTS = \
+	--volume $(CI_SCRATCHDIR)/group:/etc/group:ro,z \
+	--volume $(CI_SCRATCHDIR)/passwd:/etc/passwd:ro,z \
+	$(NULL)
+
+# Docker containers can have very large ulimits
+# for nofiles - as much as 1048576. This makes
+# libvirt very slow at exec'ing programs.
+CI_ULIMIT_FILES = 1024
+
+# Args to use when cloning a git repo.
+#  -c  stop it complaining about checking out a random hash
+#  -q  stop it displaying progress info for local clone
+#  --local ensure we don't actually copy files
+CI_GIT_ARGS = \
+	-c advice.detachedHead=false \
+	-q \
+	--local  \
+	$(NULL)
+
+# Args to use when running the Docker env
+#   --rm      stop inactive containers getting left behind
+#   --user    we execute as the same user & group account
+#             as dev so that file ownership matches host
+#             instead of root:root
+#   --volume  to pass in the cloned git repo & config
+#   --workdir to set cwd to vpath build location
+#   --ulimit  lower files limit for performance reasons
+#   --interactive
+#   --tty     Ensure we have ability to Ctrl-C the build
+CI_DOCKER_ARGS = \
+	--rm \
+	--user $(CI_UID):$(CI_GID) \
+	--interactive \
+	--tty \
+	$(CI_PWDB_MOUNTS) \
+	--volume $(CI_HOST_SRCDIR):$(CI_CONT_SRCDIR):z \
+	--workdir $(CI_CONT_SRCDIR) \
+	--ulimit nofile=$(CI_ULIMIT_FILES):$(CI_ULIMIT_FILES) \
+	$(NULL)
+
+ci-check-docker:
+	@echo -n "Checking if Docker is available and running..." && \
+	docker version 1>/dev/null && echo "yes"
+
+ci-prepare-tree: ci-check-docker
+	@test "$(CI_REUSE)" != "1" && rm -rf $(CI_SCRATCHDIR) || :
+	@if ! test -d $(CI_SCRATCHDIR) ; then \
+		mkdir -p $(CI_SCRATCHDIR); \
+		cp /etc/passwd $(CI_SCRATCHDIR); \
+		cp /etc/group $(CI_SCRATCHDIR); \
+		echo "Cloning $(CI_GIT_ROOT) to $(CI_HOST_SRCDIR)"; \
+		git clone $(CI_GIT_ARGS) $(CI_GIT_ROOT) $(CI_HOST_SRCDIR) || exit 1; \
+		for mod in $(CI_SUBMODULES) ; \
+		do \
+			test -f $(CI_GIT_ROOT)/$$mod/.git || continue ; \
+			echo "Cloning $(CI_GIT_ROOT)/$$mod to $(CI_HOST_SRCDIR)/$$mod"; \
+			git clone $(CI_GIT_ARGS) $(CI_GIT_ROOT)/$$mod $(CI_HOST_SRCDIR)/$$mod || exit 1; \
+		done ; \
+	fi
+
+# $CONFIGURE_OPTS is a env that can optionally be set in the container,
+# populated at build time from the Dockerfile. A typical use case would
+# be to pass --host/--target args to trigger cross-compilation
+#
+# This can be augmented by make local args in $(CI_CONFIGURE_ARGS)
+#
+# gl_public_submodule_commit= to disable gnulib's submodule check
+# which breaks due to way we clone the submodules
+ci-build@%: ci-prepare-tree
+	docker run $(CI_DOCKER_ARGS) $(CI_IMAGE_PREFIX)$*$(CI_IMAGE_TAG) \
+		/bin/bash -c '\
+		mkdir -p $(CI_CONT_BUILDDIR) || exit 1 ; \
+		cd $(CI_CONT_BUILDDIR) ; \
+		NOCONFIGURE=1 $(CI_CONT_SRCDIR)/autogen.sh || exit 1 ; \
+		$(CI_CONFIGURE) $${CONFIGURE_OPTS} $(CI_CONFIGURE_ARGS) ; \
+		if test $$? != 0 ; \
+		then \
+			test -f config.log && cat config.log ; \
+			exit 1 ; \
+		fi; \
+		find -name test-suite.log -delete ; \
+		export VIR_TEST_DEBUG=1 ; \
+		make -j$(CI_SMP) gl_public_submodule_commit= $(CI_MAKE_ARGS) ; \
+		if test $$? != 0 ; then \
+			LOGS=`find -name test-suite.log` ; \
+			if test "$${LOGS}" != "" ; then \
+				echo "=== LOG FILE(S) START ===" ; \
+				cat $${LOGS} ; \
+				echo "=== LOG FILE(S) END ===" ; \
+			fi ; \
+			exit 1 ;\
+		fi'
+	@test "$(CI_CLEAN)" = "1" && rm -rf $(CI_SCRATCHDIR) || :
+
+ci-check@%:
+	$(MAKE) -f $(CI_MAKEFILE) ci-build@$* CI_MAKE_ARGS="check"
+
+ci-shell@%: ci-prepare-tree
+	docker run $(CI_DOCKER_ARGS) $(CI_IMAGE_PREFIX)$*$(CI_IMAGE_TAG) /bin/bash
+	@test "$(CI_CLEAN)" = "1" && rm -rf $(CI_SCRATCHDIR) || :
+
+ci-help:
+	@echo "Build libvirt inside Docker containers used for CI"
+	@echo
+	@echo "Available targets:"
+	@echo
+	@echo "    ci-build@\$$IMAGE - run a default 'make'"
+	@echo "    ci-check@\$$IMAGE - run a 'make check'"
+	@echo "    ci-shell@\$$IMAGE - run an interactive shell"
+	@echo
+	@echo "Available x86 container images:"
+	@echo
+	@echo "    centos-7"
+	@echo "    debian-9"
+	@echo "    debian-sid"
+	@echo "    fedora-28"
+	@echo "    fedora-29"
+	@echo "    fedora-rawhide"
+	@echo "    ubuntu-18"
+	@echo
+	@echo "Available cross-compiler container images:"
+	@echo
+	@echo "    debian-{9,sid}-cross-aarch64"
+	@echo "    debian-{9,sid}-cross-armv6l"
+	@echo "    debian-{9,sid}-cross-armv7l"
+	@echo "    debian-sid-cross-i686"
+	@echo "    debian-{9,sid}-cross-mips64el"
+	@echo "    debian-{9,sid}-cross-mips"
+	@echo "    debian-{9,sid}-cross-mipsel"
+	@echo "    debian-{9,sid}-cross-ppc64le"
+	@echo "    debian-{9,sid}-cross-s390x"
+	@echo
+	@echo "Available make variables:"
+	@echo
+	@echo "    CI_CLEAN=0 - do not delete '$(CI_SCRATCHDIR)' after completion"
+	@echo "    CI_REUSE=1 - re-use existing '$(CI_SCRATCHDIR)' content"
+	@echo