Update third_party/wuffs version

Wuffs ships as a "single file C library". Previously, that single file
was a .h file. Now it is a .c file.

The contents of the file are practically the same. The different file
name extension means that the build system (GN/ninja) will treat that
file as a .c file, or "something that generates code", and not merely a
.h file, or "something #include'd by things that generate code".

This should hopefully fix mysterious linker errors when updating the
third_party/wuffs checkout results in the builder doing no work, since
no .c files changed.

Bug: skia:8235
Change-Id: I451e251d8cd23f3f0db359bbe03caa429c00fcea
Reviewed-on: https://skia-review.googlesource.com/c/180420
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
diff --git a/DEPS b/DEPS
index 9606bff..2fabf23 100644
--- a/DEPS
+++ b/DEPS
@@ -31,7 +31,7 @@
   "third_party/externals/spirv-tools"     : "https://skia.googlesource.com/external/github.com/KhronosGroup/SPIRV-Tools.git@e9e4393b1c5aad7553c05782acefbe32b42644bd",
   "third_party/externals/swiftshader"     : "https://swiftshader.googlesource.com/SwiftShader@050698222644f3dd4c022720f8298075763585be",
   #"third_party/externals/v8"              : "https://chromium.googlesource.com/v8/v8.git@5f1ae66d5634e43563b2d25ea652dfb94c31a3b4",
-  "third_party/externals/wuffs"           : "https://github.com/google/wuffs.git@f51c71b72cfc3ce3515d1196eb78f0a64c9955ff",
+  "third_party/externals/wuffs"           : "https://github.com/google/wuffs.git@bdd31a2dc880d06c6ec8f4c64ca94074d0427350",
   "third_party/externals/zlib"            : "https://chromium.googlesource.com/chromium/src/third_party/zlib@47af7c547f8551bd25424e56354a2ae1e9062859",
   "third_party/externals/Nima-Cpp"      : "https://github.com/2d-inc/Nima-Cpp.git@4bd02269d7d1d2e650950411325eafa15defb084",
   "third_party/externals/Nima-Math-Cpp" : "https://github.com/2d-inc/Nima-Math-Cpp.git@e0c12772093fa8860f55358274515b86885f0108",