> Those '*.cmake' files only work with CMake, which is an issue if you try using any other build system.

At least meson can parse those. Making every other build system in existence add support for those is definitely less work than changing the format of .a and will yield exactly the same result (not that it matters much, cmake being the standard c/c++ build system for years now)

Also .pc files are near inexistent on the most used desktop OS.