aclocal: Use -Werror when checking compiler flags (try 2)

[Per Johansson]

...if supported by compiler.
This makes clang exit with error on unsupported warnings.
---
 aclocal.m4   | 2 +-
 configure.ac | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/aclocal.m4 b/aclocal.m4
index 14cf916..a6d9f12 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -74,7 +74,7 @@ AC_DEFUN([WINE_TRY_CFLAGS],
 [AS_VAR_PUSHDEF([ac_var], ac_cv_cflags_[[$1]])dnl
 AC_CACHE_CHECK([whether the compiler supports $1], ac_var,
 [ac_wine_try_cflags_saved=$CFLAGS
-CFLAGS="$CFLAGS $1"
+CFLAGS="$CFLAGS $ac_wine_try_cflags_werror $1"
 AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(int argc, char **argv) { return 0; }]])],
                [AS_VAR_SET(ac_var,yes)], [AS_VAR_SET(ac_var,no)])
 CFLAGS=$ac_wine_try_cflags_saved])
diff --git a/configure.ac b/configure.ac
index 77ee82d..adf3148 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1742,6 +1742,7 @@ then
   fi
 
   dnl Check for some compiler flags
+  WINE_TRY_CFLAGS([-Werror],[ac_wine_try_cflags_werror=-Werror])
   WINE_TRY_CFLAGS([-fno-builtin],[AC_SUBST(BUILTINFLAG,"-fno-builtin")])
   WINE_TRY_CFLAGS([-fno-strict-aliasing])
   WINE_TRY_CFLAGS([-Wdeclaration-after-statement])
-- 
1.8.0.2