contrib: png: build 1.6.38 with CMake
And don't depend on an outdated automake 1.11 version.
v7:
- only use
gas-preprocessor.pl
forios-armv7
in CMake - don't build
gas-preprocessor.pl
forios-arm64
(as it was before)
v8:
- only force NEON build when gas-preprocessor is used as detection fails without it
v9:
- force NEON on macOS/iOS arm64 as well as it was working that way and doesn't with automatic detection
Edited by Steve Lhomme