build-mingw-w64: Update the mingw-w64 version

This version contains fixes for wchar printf functions in how they
handle %s/%S formats.

This isn't the absolute latest version, as there's other commits further
ahead adding support for _FORTIFY_SOURCE (which has little to no effect
with Clang as it doesn't evaluate __builtin_object_size in inlined
contexts), and the commits for _FORTIFY_SOURCE caused a few regressions,
and things might still be a bit in flux (even though the current master
seems to work fine).

build-mingw-w64.sh

@@ -54,7 +54,7 @@ cd mingw-w64
 
 if [ -n "$SYNC" ] || [ -n "$CHECKOUT" ]; then
     [ -z "$SYNC" ] || git fetch
-    git checkout d8ed328d4656cc467d692e1c5bd2dc7007695ef8
+    git checkout 0a1d495478d8ed1a94fc77b9dbb428b7e0372588
 fi
 
 # If crosscompiling the toolchain itself, we already have a mingw-w64