Shorten brew tests temporary paths.

[MikeMcQuaid]

If you have HOMEBREW_TEMP set to a longer path (e.g. the user's private temporary directory rather than /private/tmp), Sequoia will error out on some tests when forking because the path is too long (> 104 bytes).

To improve this situation let's:

• use a shorter path for HOMEBREW_TEMP by appending /brew-tests to the existing HOMEBREW_TEMP used outside of tests rather than creating nested temporary directories
• use the minimal amount of randomness to avoid collisions while allowing parallel tests
• use squeeze to remove any double slashes in the temporary path

[Bo98]

Sequoia will error out on some tests when forking because the path is too long (> 104 bytes).

Note that macOS has an extension to BSD sockets that does support up to 253 characters, but that extension is not properly exposed in Ruby so requires a wrapper:

class UNIXServerExt < Socket
  attr_reader :path

  def initialize(path)
    super(:UNIX, :STREAM)
    bind("\x01\x00" + path)
    listen(Socket::SOMAXCONN)
    @path = path
  end
end

If you'd like to go that route instead: let me know and I can open a PR to do that today.

[MikeMcQuaid]

If you'd like to go that route instead: let me know and I can open a PR to do that today.

@Bo98 Yes, please. Merging this to unblock brew tests on Sequoia in these configurations but please feel free to revert any/all of this PR if it's no longer needed.

[MikeMcQuaid]

(@Bo98 it may also be that this stuff is worth attempting to upstream once it's working for us)