qga: Make qemu-ga compile statically for Windows

Attempting to compile qemu-ga statically as follows for Windows causes
the following error:

Compilation:
    ./configure --disable-docs --target-list=x86_64-softmmu \
    --cross-prefix=x86_64-w64-mingw32- --static \
    --enable-guest-agent-msi --with-vss-sdk=/path/to/VSSSDK72

    make -j8 qemu-ga

Error:
    path/to/qemu/stubs/error-printf.c:7: undefined reference to `__imp_g_test_config_vars'
    collect2: error: ld returned 1 exit status
    Makefile:444: recipe for target 'qemu-ga.exe' failed
    make: *** [qemu-ga.exe] Error 1

This is caused by a bug in the pkg-config file for glib as it doesn't define
GLIB_STATIC_COMPILATION for pkg-config --static.

Signed-off-by: Sameeh Jubran <sameeh@daynix.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

configure

@@ -3066,6 +3066,13 @@ if test "$modules" = yes; then
     glib_modules="$glib_modules gmodule-2.0"
 fi
 
+# This workaround is required due to a bug in pkg-config file for glib as it
+# doesn't define GLIB_STATIC_COMPILATION for pkg-config --static
+
+if test "$static" = yes -a "$mingw32" = yes; then
+    QEMU_CFLAGS="-DGLIB_STATIC_COMPILATION $QEMU_CFLAGS"
+fi
+
 for i in $glib_modules; do
     if $pkg_config --atleast-version=$glib_req_ver $i; then
         glib_cflags=$($pkg_config --cflags $i)