[lasem] Adopt GNOME compile warnings (if available)

[J.H.M. Dassen (Ray) <jdassen src gnome org>]

commit 2b7bf53a74bd36b4f7a1c9cce5f2d67c1465d71e
Author: J.H.M. Dassen (Ray) <jdassen debian org>
Date:   Tue Jan 1 12:17:02 2013 +0100

    Adopt GNOME compile warnings (if available)

 configure.ac |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index f723a31..660d965 100644
--- a/configure.ac
+++ b/configure.ac
@@ -47,6 +47,12 @@ PKG_CHECK_MODULES(LASEM, [gobject-2.0
 # a pkgconfig file.
 LASEM_LIBS="${LASEM_LIBS} -lm"
 
+## this should come after `AC_PROG_CC'
+ifdef([GNOME_COMPILE_WARNINGS],
+	[GNOME_COMPILE_WARNINGS] CFLAGS="$CFLAGS $WARN_CFLAGS",
+	[]
+)
+
 AC_SUBST(LASEM_CFLAGS)
 AC_SUBST(LASEM_LIBS)