Scallywag GH Actions CI Cygwin release installed 3.5.7 not 3.6.1

[Jon Turney]

On 13/04/2025 16:04, Brian Inglis via Cygwin-apps wrote:
> Hi folks,
> 
> Should we not be running with Cygwin release 3.6.1 now?
> 

Ideally, yes.

But this seems contraindicated if that's going to generate packages with 
incorrect permissions, which seems to be the case.

(See https://cygwin.com/pipermail/cygwin/2025-April/257942.html)

I *suspect* this needs an extra step in scallwag to remove inheritable 
ACL permissions before we start the build.

Once I have had a chance to try that and verify it fixes the problem, 
I'll remove the pin to 3.5.7