#285 libpng 1.6.36 testsuite failure on macOS 10.14 (Mojave)

[FX]

libpng 1.6.36 testsuite fails on macOS 10.14.2 (macOS Mojave, the latest macOS version):

FAIL: tests/pngtest
===================

 Testing libpng version 1.6.36
   with zlib   version 1.2.11

libpng version 1.6.36
Copyright (c) 2018 Cosmin Truta
Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
Copyright (c) 1996-1997 Andreas Dilger
Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 library (10636): libpng version 1.6.36 - December 1, 2018

 pngtest (10636): libpng version 1.6.36 - December 1, 2018

 Testing ./pngtest.png:
   Text compression[0]=-1

 stereo mode = 1
 vpAg = 100 x 100, units = 0

   Text compression[0]=0
 eXIf type MM, 52 bytes

 Image width = 91, height = 69

Files ./pngtest.png and pngout.png are of a different size
   Was ./pngtest.png written with the same maximum IDAT chunk size (8192 bytes),
   filtering heuristic (libpng default), compression level (zlib default),
   and zlib version (1.2.11)?

 FAIL
 libpng FAILS test
 Default limits:
  width_max  = 1000000
  height_max = 1000000
  cache_max  = 1000
  malloc_max = 8000000
FAIL tests/pngtest (exit status: 1)

This was observed as part of Homebrew testing: https://github.com/Homebrew/homebrew-core/pull/34765