libc/mingw: do not remove support symlink

Under mingw, it seems that there is a mix between the traditional /usr
directory, and a similar-purposed /mingw directory (both in the sysroot).

Currently, we create /mingw as a symlink to /usr, and we removed it in
the libc-finish step.

Unfortunately, this prevents the pre-processor to find the headers.
Keeping the symlink makes it magically work...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
(transplanted from fa5c70b11fecf390c78780fe8f8ba0a836a59e92)

diff -durN gcc-3.4.6.orig/gcc/config/sh/sh.h gcc-3.4.6/gcc/config/sh/sh.h

--- gcc-3.4.6.orig/gcc/config/sh/sh.h	2006-01-12 02:20:32.000000000 +0100

+++ gcc-3.4.6/gcc/config/sh/sh.h	2007-08-15 23:03:09.000000000 +0200

@@ -422,6 +422,10 @@

 do {									\

   if (LEVEL)								\

     flag_omit_frame_pointer = -1;					\

+  if (LEVEL <= 2)							\

+    {									\

+      flag_reorder_blocks = 0;						\

+    }									\

   if (SIZE)								\

     target_flags |= SPACE_BIT;						\

   if (TARGET_SHMEDIA && LEVEL > 1)					\