Enable SIMD support for Windows on ARM

This enables SIMD support for Windows on ARM devices.

Patch submitted by Pierrick Bouvier <pierrick.bouvier@linaro.org>

Bug: https://github.com/flutter/flutter/issues/62597
Change-Id: I5480cb20f22fc14770df7bd6a305fdabe8755ef3
Reviewed-on: https://flutter-review.googlesource.com/c/third_party/libpng/+/34461
Commit-Queue: Chris Bracken <cbracken@google.com>
Reviewed-by: Jason Simmons <jsimmons@google.com>
Reviewed-by: Zach Anderson <zra@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index a875a36..eb04ba2 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -30,7 +30,7 @@
     "pngwutil.c",
   ]
 
-  if ((is_android || is_linux || is_fuchsia || is_ios || is_mac) &&
+  if ((is_android || is_linux || is_fuchsia || is_ios || is_mac || is_win) &&
        (current_cpu == "arm" || current_cpu == "arm64")) {
     sources += [
       "arm/arm_init.c",