modules: do not include gmodule-2.0 in static builds

gmodule-2.0's pkg-config files include -Wl,--export-dynamic, which breaks
static builds.  It is a glib bug, but we need to support --static builds for
the linux-user targets, and in the end all that is needed to fix this is:

* outlaw --enable-modules --static, which makes little sense anyway

* only include gmodule-2.0's cflags and ldflags if --enable-modules is
specified on the command line.
Reported-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-id: 1393346215-5636-1-git-send-email-pbonzini@redhat.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

configure

@@ -1424,6 +1424,9 @@ if compile_prog "-Werror -fno-gcse" "" ; then
 fi
 
 if test "$static" = "yes" ; then
+  if test "$modules" = "yes" ; then
+    error_exit "static and modules are mutually incompatible"
+  fi
   if test "$pie" = "yes" ; then
     error_exit "static and pie are mutually incompatible"
   else
@@ -2483,8 +2486,12 @@ if test "$mingw32" = yes; then
 else
     glib_req_ver=2.12
 fi
+glib_modules=gthread-2.0
+if test "$modules" = yes; then
+    glib_modules="$glib_modules gmodule-2.0"
+fi
 
-for i in gthread-2.0 gmodule-2.0; do
+for i in $glib_modules; do
     if $pkg_config --atleast-version=$glib_req_ver $i; then
         glib_cflags=`$pkg_config --cflags $i`
         glib_libs=`$pkg_config --libs $i`

util/module.c

@@ -14,7 +14,9 @@
  */
 
 #include <stdlib.h>
+#ifdef CONFIG_MODULES
 #include <gmodule.h>
+#endif
 #include "qemu-common.h"
 #include "qemu/queue.h"
 #include "qemu/module.h"