Add regression test for #20568

GHC produced broken executables with rebindable if and -fhpc if ifThenElse expected non-Bool condition until GHC 9.0. This MR adds a simple regression test.

mentioned in issue #20568 (closed)

approved this merge request

assigned to @marge-bot

I will attempt to batch this MR (!6925 (closed))...

Merged in 6f2d6a5d

closed