Add chibicc

This program popped up on Hacker News recently. It's the only modern
compiler I've ever seen that doesn't have dependencies and is easily
modified. So I added all of the missing GNU extensions I like to use
which means it might be possible soon to build on non-Linux and have
third party not vendor gcc binaries.

libc/log/verrx.c

@@ -23,7 +23,7 @@
 #include "libc/runtime/runtime.h"
 #include "libc/stdio/stdio.h"
 
-noreturn void(verrx)(int eval, const char *fmt, va_list va) {
+wontreturn void(verrx)(int eval, const char *fmt, va_list va) {
   fprintf(stderr, "%s: %s%s%s: ", program_invocation_name, RED2, "ERROR",
           RESET);
   if (fmt) (vfprintf)(stderr, fmt, va);