Find clang-format on macOS

[stephane-caron]

@boragokbakan Could you try out this branch and let me know if it works for you?

[coveralls]

Pull Request Test Coverage Report for Build 4861708232

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 82.472%

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Totals
Change from base Build 4852982748:	0.0%
Covered Lines:	1341
Relevant Lines:	1626

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💛 - Coveralls

[ubgk]

It didn't match my executable path, so I made a small fix: #20