gcc-8 is smarter about possible overflow detection.

Reported-by: Mike Lothian
Bug: https://bugs.gentoo.org/654724
--- a/webserver/Makefile
+++ b/webserver/Makefile
@@ -5 +5 @@ SOURCES = main.c mongoose.c
-CFLAGS = -O2 -W -Wall -Werror -Wno-unused-function $(CFLAGS_EXTRA) $(MODULE_CFLAGS)
+CFLAGS = -O2 -W -Wall -Wno-unused-function $(CFLAGS_EXTRA) $(MODULE_CFLAGS)