Oh ... one other thought, based on forcing the collate.linux.utf8
test to run on platforms where it can be expected to fail: I think
you'd be well advised to make that test verify that the required
collations are present, the same as you did in the collate.icu.utf8
test. I noticed for instance that it fails if en_US.utf8 is not
present (or not spelled exactly like that), but I doubt that that
locale is necessarily present on every Linux platform. tr_TR is
even more likely to be subject to packagers' whims.
regards, tom lane