[vte] build: m4: Fix m4 warning about missing AC_LANG_SOURCE

[Christian Persch <chpe src gnome org>]

commit 3539be453711e38858d79035867d742c534a6a1e
Author: Christian Persch <chpe gnome org>
Date:   Tue Mar 31 19:53:46 2015 +0200

    build: m4: Fix m4 warning about missing AC_LANG_SOURCE

 acinclude.m4 |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/acinclude.m4 b/acinclude.m4
index 97f094b..6f019f1 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -67,7 +67,7 @@ AC_DEFUN([CC_CHECK_LDFLAGS], [
     AS_TR_SH([cc_cv_ldflags_$1]),
     [ac_save_LDFLAGS="$LDFLAGS"
      LDFLAGS="$LDFLAGS $1"
-     AC_LINK_IFELSE([int main() { return 1; }],
+     AC_LINK_IFELSE([AC_LANG_SOURCE([int main() { return 1; }])],
        [eval "AS_TR_SH([cc_cv_ldflags_$1])='yes'"],
        [eval "AS_TR_SH([cc_cv_ldflags_$1])="])
      LDFLAGS="$ac_save_LDFLAGS"