cc/gcc: fix thread-less final gcc build

If threads are disabled in libc, we don't want to enable them in the
final compiler. Doing so pass the configure stage, but fails latter on
a missing <pthread.h>.

Moreover, we don't want to build libgomp if threads are disabled; its
configure script would fails anyway.

Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>

--- gcc-4.0.0/libstdc++-v3/include/c_std/std_cstdio.h-orig	2005-04-29 00:08:41.000000000 -0500

+++ gcc-4.0.0/libstdc++-v3/include/c_std/std_cstdio.h	2005-04-29 00:08:45.000000000 -0500

@@ -142,7 +142,7 @@

   using ::vsprintf;

 }

-#if _GLIBCXX_USE_C99

+#if _GLIBCXX_USE_C99 || defined(__UCLIBC__)

 #undef snprintf

 #undef vfscanf