install-wrappers: Use llvm-windres if available

If the llvm-windres tool is available, use that instead of our own
wrapper that calls clang, llvm-rc and llvm-cvtres separately.

install-wrappers.sh

@@ -93,9 +93,13 @@ for arch in $ARCHS; do
             fi
             ln -sf $link_target$EXEEXT $arch-w64-$target_os-$exec$EXEEXT || true
         done
-        for exec in windres; do
-            ln -sf $exec-wrapper$EXEEXT $arch-w64-$target_os-$exec$EXEEXT
-        done
+        if [ -f "llvm-windres$EXEEXT" ]; then
+            # windres can't use llvm-wrapper, as that loses the original
+            # target arch prefix.
+            ln -sf llvm-windres$EXEEXT $arch-w64-$target_os-windres$EXEEXT
+        else
+            ln -sf windres-wrapper$EXEEXT $arch-w64-$target_os-windres$EXEEXT
+        fi
         for exec in ld objdump dlltool; do
             ln -sf $exec-wrapper.sh $arch-w64-$target_os-$exec
         done