rpm: disable netcf for the interface driver in rpm build on new targets

libvirt.spec currently adds a hardcoded -Dnetcf=enabled to the meson
commandline, so just setting the default in the meson.build file won't
have any effect for rpm builds - it will be overridden.

This patch changes the meson commandline in the spec file from
hardcoded -Dnetcf=enabled to %{arg_netcf}, which is itself set
according to the value of %{with_netcf}; and *that* is normally set
according to the distro release of the build target (1 for Fedora >=
34 and RHEL >= 9, 0 otherwise), but can be manually overridden by
adding "-without netcf" to the rpmbuild commandline.

Along with being used to determine what arg to pass to meson,
%{with_netcf} is also checked when deciding on whether or not to add
netcf build time / install time dependencies ("Requires: netcf-libs"
and "BuildRequires: netcf-devel")

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Neal Gompa <ngompa13@gmail.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

libvirt.spec.in

@@ -101,6 +101,7 @@
 %define with_sanlock          0
 %define with_numad            0
 %define with_firewalld_zone   0
+%define with_netcf            0
 %define with_libssh2          0
 %define with_wireshark        0
 %define with_libssh           0
@@ -145,6 +146,10 @@
     %define with_firewalld_zone 0%{!?_without_firewalld_zone:1}
 %endif
 
+%if 0%{?fedora} < 34 || 0%{?rhel} < 9
+    %define with_netcf 0%{!?_without_netcf:1}
+%endif
+
 
 # fuse is used to provide virtualized /proc for LXC
 %if %{with_lxc}
@@ -357,8 +362,9 @@ BuildRequires: fuse-devel >= 2.8.6
 %if %{with_libssh2}
 BuildRequires: libssh2-devel >= 1.3.0
 %endif
-
+%if %{with_netcf}
 BuildRequires: netcf-devel >= 0.2.2
+%endif
 %if %{with_esx}
 BuildRequires: libcurl-devel
 %endif
@@ -527,13 +533,13 @@ capabilities.
 Summary: Interface driver plugin for the libvirtd daemon
 Requires: libvirt-daemon = %{version}-%{release}
 Requires: libvirt-libs = %{version}-%{release}
+%if %{with_netcf}
 Requires: netcf-libs >= 0.2.2
+%endif
 
 %description daemon-driver-interface
 The interface driver plugin for the libvirtd daemon, providing
-an implementation of the network interface APIs using the
+an implementation of the host network interface APIs.
-netcf library
-
 
 %package daemon-driver-secret
 Summary: Secret driver plugin for the libvirtd daemon
@@ -1099,6 +1105,12 @@ exit 1
     %define arg_firewalld_zone -Dfirewalld_zone=disabled
 %endif
 
+%if %{with_netcf}
+    %define arg_netcf -Dnetcf=enabled
+%else
+    %define arg_netcf -Dnetcf=disabled
+%endif
+
 %if %{with_wireshark}
     %define arg_wireshark -Dwireshark_dissector=enabled
 %else
@@ -1169,7 +1181,7 @@ export SOURCE_DATE_EPOCH=$(stat --printf='%Y' %{_specdir}/%{name}.spec)
            %{?arg_numad} \
            -Dcapng=enabled \
            %{?arg_fuse} \
-           -Dnetcf=enabled \
+           %{?arg_netcf} \
            -Dselinux=enabled \
            %{?arg_selinux_mount} \
            -Dapparmor=disabled \