yt-dlp: use gmake for head build

[Wallunen]

• Have you followed the guidelines for contributing?
• Have you ensured that your commits follow the commit style guide?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>)? If this is a new formula, does it pass brew audit --new <formula>?

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yt-dlp/yt-dlp#9210

[ZhongRuoyu]

Does it actually fail when using make instead of gmake? Because GNU Make is already provided by macOS, and also required by Linuxbrew. I don't think we're using BSD Make anywhere.

[Wallunen]

Does it actually fail when using make instead of gmake? Because GNU Make is already provided by macOS, and also required by Linuxbrew. I don't think we're using BSD Make anywhere.

It does fail on my Mac where /usr/bin/make is version 3.81.

[ZhongRuoyu]

Thanks, @Wallunen.