roll libpng to pre-1.6.38

This rolls in the patch to fix NEON + clang-cl.

Cq-Include-Trybots: skia.primary:Build-Win-Clang-arm64-Release
Change-Id: Id34730763ff56b89bb49033001ffb42b09d55a61
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210360
Commit-Queue: Mike Klein <mtklein@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
diff --git a/DEPS b/DEPS
index 7a6c93e..f37c891 100644
--- a/DEPS
+++ b/DEPS
@@ -16,7 +16,7 @@
   "third_party/externals/icu"             : "https://chromium.googlesource.com/chromium/deps/icu.git@407b39301e71006b68bd38e770f35d32398a7b14",
   "third_party/externals/imgui"           : "https://skia.googlesource.com/external/github.com/ocornut/imgui.git@d38d7c6628bebd02692cfdd6fa76b4d992a35b75",
   "third_party/externals/libjpeg-turbo"   : "https://skia.googlesource.com/external/github.com/libjpeg-turbo/libjpeg-turbo.git@2.0.0",
-  "third_party/externals/libpng"          : "https://skia.googlesource.com/third_party/libpng.git@v1.6.37",
+  "third_party/externals/libpng"          : "https://skia.googlesource.com/third_party/libpng.git@386707c6d19b974ca2e3db7f5c61873813c6fe44",
   "third_party/externals/libwebp"         : "https://chromium.googlesource.com/webm/libwebp.git@v1.0.2-rc1",
   "third_party/externals/lua"             : "https://skia.googlesource.com/external/github.com/lua/lua.git@v5-3-4",
   "third_party/externals/microhttpd"      : "https://android.googlesource.com/platform/external/libmicrohttpd@748945ec6f1c67b7efc934ab0808e1d32f2fb98d",