lib: Fix Homebrew/NoFileutilsRmrf RuboCop offenses

[issyl0]

• 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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• Part of rubocop: Discourage the use of rm_f and rm_rf in formulae and casks brew#17705.
• Different approach from the previous massive PR - I'm splitting them up per-alphabet letter (ish) and letting CI do the full "no bottles" build. This is lib.

[issyl0]

Full audit --formula libgccjit --online --git --skip-style output
  libgccjit
    * Stable: The source URL https://ftp.gnu.org/gnu/gcc/gcc-14.1.0/gcc-14.1.0.tar.xz is not reachable

[issyl0]

Installing that formula works for me locally. 🤷🏻 What do we usually do in these situations? It's really only CI syntax, no bottles or anything. Can we add the label and re-run the shorter tests?