Fix hipSYCL clang plugin path on MacOS

[illuhad]

@normallytangent Does this help with accelerated CPU on Apple?

[normallytangent]

Confusingly, it does not. I tested it with accelerated cpu set to On. I get the same error I showed earlier but now if complains it can't find hipSYCL_clang.dylib file even though it is already there at the same path the error message is about.

[illuhad]

That's weird... Can you please send me the error, or post it somewhere?

[fodinabor]

Uhh, nice! :)

One thing that's slightly related, which I learned in the meantime, and I just wanted to note: the plugin-style dynamic libraries like libhipSYCL_clang.so or libhipSYCL_omp.so usually are (should be) declared with add_library(<name> MODULE <src>).
See https://cmake.org/cmake/help/latest/command/add_library.html and maybe https://stackoverflow.com/questions/4845984/difference-between-modules-and-shared-libraries
Doesn't make much of a functional difference. On MacOS MODULE libraries will be .so files instead of .dylib, though.

[normallytangent]

I tested it once more, all the tests pass with accelerated cpu.