Kind of get bash to compile

Doesn't link yet due to "multiple definitions of malloc", because some are supplied by some library of bash itself. Really odd.

include/bits/unistd.h

@@ -1,6 +1,8 @@
 #ifndef _BITS_UNISTD_H
 #define _BITS_UNISTD_H
 
+#define _POSIX_VERSION 200809L
+
 int execl(const char *path, const char* argv0, ...);
 int execle(const char *path, const char* argv0, ...);