build: Use -Wvariadic-macros warning

acinclude.m4

@@ -58,6 +58,7 @@ AC_DEFUN([COMPILER_FLAGS], [
 		CFLAGS+=" -Wdeclaration-after-statement"
 		CFLAGS+=" -Wmissing-declarations"
 		CFLAGS+=" -Wredundant-decls"
+		CFALGS+=" -Wvariadic-macros"
 		CFLAGS+=" -Wformat -Wformat-security"
 		if ( $CC -v 2>/dev/null | grep "gcc version" ); then
 			CFLAGS+=" -Wcast-align"