Reinstate bloody warning

Author: Girgias

Zend/Zend.m4

@@ -216,7 +216,7 @@ test -n "$GCC" && CFLAGS="$CFLAGS -Wall -Wextra -Wno-strict-aliasing -Wno-implic
 dnl Check if compiler supports -Wno-clobbered (only GCC)
 AX_CHECK_COMPILE_FLAG([-Wno-clobbered], CFLAGS="$CFLAGS -Wno-clobbered", , [-Werror])
 dnl Move -Wstrict-prototypes after because it messes with the -Wno-clobbered check
-CFLAGS = "$CFLAGS -Wstrict-prototypes"
+AX_CHECK_COMPILE_FLAG([-Wstrict-prototypes], CFLAGS="$CFLAGS -Wstrict-prototypes", , [-Werror])
 
 test -n "$DEBUG_CFLAGS" && CFLAGS="$CFLAGS $DEBUG_CFLAGS"