Build for Apple Silicon using Xcode 15

[pedrolinhares]

Description

Fixes to build on Apple Silicon using cmake's Xcode generator. Due to library being built only with OBJECT libraries, Xcode is unable to correctly build the library. In this case, we need to add at least one cpp source to the library build in order to Xcode to correctly build the target.

Fixes # (github issue)

Checklist

General

• Do all unit and benchdnn tests (make test and make test_benchdnn_*) pass locally for each commit?
• Have you formatted the code using clang-format?

Performance improvements

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New features

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Bug fixes

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RFC PR

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[vpirogov]

@pedrolinhares, thanks for bringing up the issue. Proposed solution looks a bit like a workaround, as it adds a dummy C++ file to trick XCode into doing the right thing. What would be the proper way to link object libraries with XCode?

[pedrolinhares]

@vpirogov This workaround seems to be the recommended solution. We need to add a real source since I didn't know which real source to link (since it's already in the object lib), adding a dummy cpp solves the problem. Also, from cmake's documentation:
"Some native build systems (such as Xcode) may not like targets that have only object files, so consider adding at least one real source file to any target that references $<TARGET_OBJECTS:objlib>." https://cmake.org/cmake/help/latest/command/add_library.html#object-libraries

If you could help point out which real sources to build the library with that would be ideal.