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/isystem/windows.h

@@ -110,13 +110,13 @@
 #define PWSTR          WCHAR*
 #define PZPWSTR        PWSTR*
 #define PCZPWSTR       CONST PWSTR*
-#define LPUWSTR        WCHAR aligned(1)*
-#define PUWSTR         WCHAR aligned(1)*
+#define LPUWSTR        WCHAR forcealign(1)*
+#define PUWSTR         WCHAR forcealign(1)*
 #define LPCWSTR        CONST WCHAR*
 #define PCWSTR         CONST WCHAR*
 #define PZPCWSTR       PCWSTR*
-#define LPCUWSTR       CONST WCHAR aligned(1)*
-#define PCUWSTR        CONST WCHAR aligned(1)*
+#define LPCUWSTR       CONST WCHAR forcealign(1)*
+#define PCUWSTR        CONST WCHAR forcealign(1)*
 #define PCHAR          CHAR*
 #define LPCH           CHAR*
 #define PCH            CHAR*