feat: Install an unlinked formula via brew install if --overwrite is passed

[boblail]

If the intention is to overwrite any existing links, then brew install should go on to install over an unlinked formula

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[boblail]

Hm. I don't think I understand this "Do not report this issue: you are running in an unsupported configuration.\n" error — how it's related to my tests. Does it make sense to one of the maintainers?

[Bo98]

Try temporarily add --debug to see if you get a better error.