openxr_loader DYLIB and SO versioning

[madebr]

Hello!

Reading OpenXR-Loader's CMake script, it seems like only Linux has SO versioned libraries.
Many other unix platforms also support some form of versioning.
Dylib libraries on macOS also provides versioning.

Is this expected?

[rpavlik]

We'd happily accept contributions to version the libraries on Mac, though the ABI has remained pretty stable by design.