[New cygwin version] cygwin-3.6.7

[github-actions]

Cygwin 3.6.7 release

https://github.com/cygwin/cygwin/releases/tag/cygwin-3.6.7

[dscho]

The MSYS2 PR was already approved and merged, now it's moved on to the MSYS2-packages PR as per usual.

The Git for Windows PR is also ready (overtaking the more risky git-for-windows/msys2-runtime#124), and I am in the process of deploying it via git-for-windows/MSYS2-packages#277.