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.

test/libc/str/test.mk

@@ -25,6 +25,7 @@ TEST_LIBC_STR_CHECKS =					\
 
 TEST_LIBC_STR_DIRECTDEPS =				\
 	LIBC_CALLS_HEFTY				\
+	LIBC_ALG					\
 	LIBC_FMT					\
 	LIBC_NEXGEN32E					\
 	LIBC_STDIO					\