Status of the hotspot repo in the build-infra forest

[Magnus Ihse Bursie]

The hotspot repo has for a long time been problematic for build-infra, 
since we have not really kept it up-to-date -- changes in 
build-infra/hotspot has not been pushed properly, and we have diverted 
from upstream hotspot, which made new fixes require additional manual 
work to sort out, with the added risk of human errors.

I have now done a thourough analysis of the hotspot situation. This is 
my findings: We have two sets of differences, compared to hotspot in the 
build forest. The differences compared to hotspot-rt/hotspot are the 
same, apart from the new stuff in hotspot-rt that has not yet reached 
build/hotspot.

The two differences are:
* The incomplete Queens/test-in-build patch, which is complete and 
correct on build-infra, but not the build forest.
* A patch to allow build-infra to run on msys.

I have sent Kelly a patch that will compensate for the first.

I have sent a webrev for the second. If there is any problem with this, 
we can skip it for now -- the "only" thing that happens is that the new 
build won't be able to build on msys in mainline. It's unfortunately, 
but it's not a regression since we've never had msys support there before.

/Magnus