gcc: Add GCC 4.6 patches from official openwrt.git toolchain directory.

Signed-off-by: Christian Beier <dontmind@freeshell.org>

devel/gcc/patches/920-specs_nonfatal_getenv.patch

@@ -0,0 +1,14 @@
+--- a/gcc/gcc.c
++++ b/gcc/gcc.c
+@@ -7772,7 +7772,10 @@ getenv_spec_function (int argc, const ch
+ 
+   value = getenv (argv[0]);
+   if (!value)
+-    fatal_error ("environment variable %qs not defined", argv[0]);
++    {
++      warning (0, "environment variable %qs not defined", argv[0]);
++      value = "";
++    }
+ 
+   /* We have to escape every character of the environment variable so
+      they are not interpreted as active spec characters.  A