cmd/go: convert TestCaseCollisions to the script framework
I'm planning to modify this test in a follow-up CL, so we might
as well convert it to a script test. I don't think there's an easy
way to detect whether we have a case-insensitive file system, without
adding a new condition to the script framework, so the test is just
guessing that darwin and windows could have case-insensitive file systems.
Change-Id: I48bb36f86f19898618681515ac448c3bb4735857
Reviewed-on: https://go-review.googlesource.com/c/go/+/228783
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Jay Conrod <jayconrod@google.com>