[2.2, DO NOT MERGE] Revert "Merge pull request #4874 from zw3rk/feature/basedir"

[23Skidoo]

This reverts commit 783cbe6, reversing changes made to c094940.

The basedir patch breaks GHC (see #5075 (comment)), so unless that issue gets fixed soon (@alpmestan, @angerman and @hvr are looking into it) we'll have to revert it on the 2.2 branch to unblock the 8.4.1 release.

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[23Skidoo]

/cc @bgamari

[23Skidoo]

To make it clear: this is plan B in case plan A (merging https://phabricator.haskell.org/D4453) doesn't work.

[angerman]

Current phabricator CI status:

• Windows: OK
• Linux: Waiting to build.
• macOS: some ext-int failures (which I can not locally reproduce on my mac...)

[hvr]

macOS: some ext-int failures (which I can not locally reproduce on my mac...)

those seem completely orthogonal to the basedir patch; what I've figured out so far is that -fexternal-interpreter indeterministically segfaults... for no apparent reason; I had to invoke ghc-stage2 in a loop for couple dozen times before it would segfault.

I expect Linux to validate just as it did before my trivial fixup/hack was applied.

[23Skidoo]

I see that D4453 has been merged, so looks like we won't need this. Closing.