[Ada] Fix compilation of raise-gcc.c with -DSTANDALONE under windows

[Pierre-Marie de Rodat via Gcc-patches]

This is needed in particular by GNAT LLVM builds.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

        * raise-gcc.c: Fix compilation with -DSTANDALONE under windows.
diff --git a/gcc/ada/raise-gcc.c b/gcc/ada/raise-gcc.c
--- a/gcc/ada/raise-gcc.c
+++ b/gcc/ada/raise-gcc.c
@@ -78,7 +78,7 @@
    (SJLJ or DWARF). We need a consistently named interface to import from
    a-except, so wrappers are defined here.  */
 
-#ifdef __CYGWIN__
+#if defined (__CYGWIN__) || (defined(__SEH__) && defined(STANDALONE))
 /* Prevent compile error due to unwind-generic.h including <windows.h>,
    see comment above #include <windows.h> in mingw32.h.  */
 #include "mingw32.h"