[patch] fix gccjit build failure

[Matthias Klose]

gccjit currently fails to build, needing an additional header. Ok to install on 
the trunk?

Matthias

        * jit-playback.c: Include <pthread.h>.

--- a/gcc/jit/jit-playback.c
+++ b/gcc/jit/jit-playback.c
@@ -43,6 +43,8 @@ along with GCC; see the file COPYING3.
 #include "jit-builtins.h"
 #include "jit-tempdir.h"

+#include <pthread.h>
+

 /* gcc::jit::playback::context::build_cast uses the convert.h API,
    which in turn requires the frontend to provide a "convert"