[network-manager-pptp] build: more flexible build-time warnings and errors options

[Dan Williams <dcbw src gnome org>]

commit ab295c94ef787533eb4dd1e9f3ff0eb099cf8504
Author: Dan Williams <dcbw redhat com>
Date:   Fri Mar 2 14:06:10 2012 -0600

    build: more flexible build-time warnings and errors options

 Makefile.am             |    2 ++
 m4/compiler_warnings.m4 |   11 +++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 1ddc292..77c38be 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -29,6 +29,8 @@ endif
 nm-pptp-service.name: $(srcdir)/nm-pptp-service.name.in
 	sed -e 's|[ ]LIBEXECDIR[@]|$(libexecdir)|g' $< >$@
 
+DISTCHECK_CONFIGURE_FLAGS = --enable-more-warnings=yes
+
 EXTRA_DIST = nm-pptp-service.name.in \
              $(dbusservice_DATA)  \
              $(desktopfile) \
diff --git a/m4/compiler_warnings.m4 b/m4/compiler_warnings.m4
index be69af2..95ad3fb 100644
--- a/m4/compiler_warnings.m4
+++ b/m4/compiler_warnings.m4
@@ -1,11 +1,11 @@
 AC_DEFUN([NM_COMPILER_WARNINGS],
 [AC_ARG_ENABLE(more-warnings,
-	AS_HELP_STRING([--enable-more-warnings], [Maximum compiler warnings]),
-	set_more_warnings="$enableval",set_more_warnings=yes)
-AC_MSG_CHECKING(for more warnings, including -Werror)
+	AS_HELP_STRING([--enable-more-warnings], [Possible values: no/yes/error]),
+	set_more_warnings="$enableval",set_more_warnings=error)
+AC_MSG_CHECKING(for more warnings)
 if test "$GCC" = "yes" -a "$set_more_warnings" != "no"; then
 	AC_MSG_RESULT(yes)
-	CFLAGS="-Wall -Werror -std=gnu89 $CFLAGS"
+	CFLAGS="-Wall -std=gnu89 $CFLAGS"
 
 	for option in -Wshadow -Wmissing-declarations -Wmissing-prototypes \
 		      -Wdeclaration-after-statement -Wstrict-prototypes \
@@ -25,6 +25,9 @@ if test "$GCC" = "yes" -a "$set_more_warnings" != "no"; then
 		unset SAVE_CFLAGS
 	done
 	unset option
+	if test "x$set_more_warnings" = xerror; then
+		CFLAGS="$CFLAGS -Werror"
+	fi
 else
 	AC_MSG_RESULT(no)
 fi