Incosistent installation path for CMake subproject shared library

[dnicolodi]

In a meson project which depends on a shared library compiled from a CMake subproject, the installation location of the CMake shared library is inconsistent between Linux and macOS hosts. On Linux it is installed in {prefix}/lib/ while on macOS it is installed in {libdir_shared}. I have no idea whether this stems from a behavior difference in CMake or if Meson is not able to correctly map the installation path on Linux.

To Reproduce
Check out the test project added to the meson-pythons test suite in this PR mesonbuild/meson-python#599 and run meson setup build. Check the installation paths in build/meson-info/intro-install_plan.json.

Expected behavior
I would expect the installation path to be the same on the two OSes. I haven't check what installation path is used on Windows.

system parameters
The Linux behavior is the same with all versions from 0.63.3 to git master. The macOS behavior has been verified with meson 1.3.0 and 1.3.2

[dnicolodi]

@dcbaker I can investigate this further. Do you have any hint about where to start to look for the source of the problem?