- s/build.yml/${build}.yml/ for the existing builds
- add filter on branches on push
- add scan-build build triggered by pushes to the scan-build branch or by PRs
that touch the scan-build.yml
- add valgrind build triggered by pushes to the valgrind branch or by PRs that
touch the valgrind.yml
We should split build.yml into separate workflows for each OS, that way
we can have Windows builds triggered by changes to NTMakefiles, but not
Linux builds.