Changes:
1. `-soname` should be `-install_name` on Darwin
2. Version suffix should placed before extension suffix (libucontext.so.1 -> libucontext.1.dylib)
3. Check for architecture specific include directory, and include it while building
4. `EXPORT_UNPREFIXED` macro shouldn't be set since Darwin don't support aliases
5. Choose correct subdir for arm64
6. Use `-dynamiclib` instead of `-shared` on Darwin for adding version info (`-current_version` and `-compatibility_version`)
Torrekie Gen