ghc: fix postinstall failure on linux

[mizunashi-mana]

• Have you followed the guidelines for contributing?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with 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 brew install <formula>)?

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Fix https://github.com/Homebrew/linuxbrew-core/issues/20475

See also NixOS/nixpkgs#85446

[jonchang]

This will need a revision bump.

[mizunashi-mana]

Test failure caused by

• Some bottles depend cabal v1 system which is deprecated: agda
• Some bottles does not support GHC 8.10: hledger

[mizunashi-mana]

This will need a revision bump.

I fixed.

[chenrui333]

for all builds

brew test --retry --verbose agda
brew test --retry --verbose agda
brew install --build-from-source bup
brew install --build-from-source hledger

for 10.15:

brew install --build-from-source bond

[chenrui333]

agda test failure is known issue, #58984