configure: introduce FLAT_NAMESPACE_FLAGS

Set FLAT_NAMESPACE_FLAGS to -Wl,-flat_namespace in configure only for
macOS and use it unconditionally in Makefiles.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

configure.ac

@@ -189,6 +189,19 @@ esac
 AC_MSG_RESULT([$VERSION_SCRIPT_FLAGS])
 AC_SUBST([VERSION_SCRIPT_FLAGS])
 
+dnl macOS has two-level namespaces by default.
+dnl Override it to allow symbol replacement with DYLD_INSERT_LIBRARIES
+case "$host" in
+  *-*-darwin*)
+    FLAT_NAMESPACE_FLAGS=-Wl,-flat_namespace
+    ;;
+  * )
+    FLAT_NAMESPACE_FLAGS=""
+    ;;
+esac
+AC_MSG_RESULT([$FLAT_NAMESPACE_FLAGS])
+AC_SUBST([FLAT_NAMESPACE_FLAGS])
+
 dnl Specify if we rely on ifconfig instead of iproute2 (e.g. in case
 dnl we're working on BSD)
 want_ifconfig=no

src/Makefile.am

@@ -431,13 +431,9 @@ libvirt_la_LDFLAGS = \
 		-version-info $(LIBVIRT_VERSION_INFO) \
 		$(LIBVIRT_NODELETE) \
 		$(NO_UNDEFINED_LDFLAGS) \
-		$(AM_LDFLAGS)
-if WITH_MACOS
-# macOS has two-level namespaces by default.
-# Override it to allow symbol replacement with DYLD_INSERT_LIBRARIES
-libvirt_la_LDFLAGS += -Wl,-flat_namespace
-endif WITH_MACOS
-libvirt_la_LDFLAGS += $(NULL)
+		$(FLAT_NAMESPACE_FLAGS) \
+		$(AM_LDFLAGS) \
+		$(NULL)
 libvirt_la_LIBADD += \
 		    $(DLOPEN_LIBS)
 libvirt_la_CFLAGS = -DIN_LIBVIRT $(AM_CFLAGS)

tests/Makefile.am

@@ -55,10 +55,9 @@ MOCKLIBS_LDFLAGS = -avoid-version \
 DRIVERLIB_LDFLAGS = \
 	-avoid-version \
 	-rpath /evil/libtool/hack/to/force/shared/lib/creation \
-	$(MINGW_EXTRA_LDFLAGS)
-if WITH_MACOS
-DRIVERLIB_LDFLAGS += -Wl,-flat_namespace
-endif WITH_MACOS
+	$(MINGW_EXTRA_LDFLAGS) \
+	$(FLAT_NAMESPACE_FLAGS) \
+	$(NULL)
 
 PROBES_O =
 if WITH_DTRACE_PROBES