Update libpng to v1.6.38 with libm cmake fix (#65)

NeroBurner · web-flow · commit 3d52e4a82610 · 2022-09-17T16:08:33.000+02:00
diff --git a/libpng b/libpng
@@ -1 +1 @@
-Subproject commit a37d4836519517bdce6cb9d956092321eca3e73b
+Subproject commit 0a158f3506502dfa23edfc42790dfaed82efba17
