Hadrian: Invoke ghc0 via bash when running tests to fix #17362.
Hadrian: Invoke ghc0 via bash when running tests to fix #17362.

cmd uses RawCommand which uses Windows semantics to find the executable
which sometimes seems to fail for unclear reasons.

If we invoke ghc via bash then bash will find the ghc executable and
the issue goes away.

sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc