Win32: set march to pentium

Fix include/vlc_atomic.h:124: undefined reference to `___sync_bool_compare_and_swap_4' etc
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

extras/package/win32/configure.sh

@@ -37,4 +37,4 @@ then
     OPTIONS="${OPTIONS} --disable-taglib --disable-mkv"
 fi
 
-sh "$(dirname $0)"/../../../configure ${OPTIONS} $*
+sh "$(dirname $0)"/../../../configure ${OPTIONS} $* CFLAGS="-march=pentium"