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/die.c

@@ -28,7 +28,7 @@
 /**
  * Aborts process after printing details on its current state.
  */
-relegated noreturn void __die(void) {
+relegated wontreturn void __die(void) {
   static bool once;
   if (!once) {
     once = true;