Xavier Claessens authored Nov 25, 2018 and Xavier Claessens committed Aug 16, 2019

This adds 3 new jobs that build against msys2 x86_64, msvc 2017 x86
and msvc 2017 x86_64. For the msvc build, some subprojects (like libnice)
don't satisfy all their deps, and are getting automatically disabled.

This doesn't add jobs that run the test suite also. Will hopefully
get implemented later on.