whisper-cpp: make compatible with --HEAD install

[mislav]

This is to accommodate the build system changes in the upcoming v1.7.4 release.

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In --HEAD mode, the main changes are that dylibs are now enabled and that the main binary is now called whisper-cli.

Libraries and header files currently unfortunately conflict with the llama.cpp formula, so in this installation we rename the "lib" folder and omit the header files to avoid the conflict. ggml-org/ggml#1050 (comment)

[mislav]

@carlocab Thanks for the detailed review; I've addressed the comments.

[carlocab]

Thanks!

[github-actions]

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