Can you reference a test package showing the problem, and a full build log?

This is the package: https://github.com/s1ddok/Cpng

After creating a system-module package for zlib I ran into two problems:

1. We don't pass pkgConfig for Clang Modules ([Build] Pass pkgconfig args when compiling ClangModule #810
2. We don't pass modulemaps of system packages to clang using -fmodule-map-file. Even after passing the modulemap file the autolinking doesn't work i.e. clang should link "z" automatically but it doesn't (unlike swiftc)

modulemap cz [system] {
link "z"
}

2. will be solved with build settings.