pull: use homebrew remote if HOMEBREW_FORCE_HOMEBREW_ON_LINUX

[dawidd6]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew tests with your changes locally?

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With this change, linux maintainers are able to perform brew pull --bottle after exporting HOMEBREW_FORCE_HOMEBREW_ON_LINUX environment variable and checking out the master branch of homebrew remote.

Successful commit example: Homebrew/homebrew-core@76bbb1d

Bottle works (thanks to @issyl0 for this):

╭─issyl0@chi /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core ‹master*› 
╰─ $ brew install findomain 
==> Downloading https://homebrew.bintray.com/bottles/findomain-1.4.1.catalina.bottle.tar.gz
==> Downloading from https://akamai.bintray.com/6f/6fb58677ebe4f07259ecb13fd99fd33f0615e299b33bd795cc1265c9e8b87a3b?__gda__=exp=1582402268~hmac=e1456e4284f4033f93611c72076d2be705ce12990172f67f51397b654765bd4
######################################################################## 100.0%
==> Pouring findomain-1.4.1.catalina.bottle.tar.gz
:beer:  /usr/local/Cellar/findomain/1.4.1: 6 files, 4.4MB
╭─issyl0@chi /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core ‹master*› 
╰─ $ brew test findomain                                                                                                                                                                                   1 ↵
Testing findomain
==> /usr/local/Cellar/findomain/1.4.1/bin/findomain -t brew.sh

[request-info]

Please provide a better issue/pull request title and/or description!

[issyl0]

This is truly life changing. Doesn't stop me wanting a Mac again tho. 😂

[MikeMcQuaid]

Thanks again @dawidd6!