Texinfo in the GitHub OS X runners must be ancient. Even Texinfo 5.1
can handle UTF-8.
```
MAKEINFO /Users/runner/work/heimdal/heimdal/doc/heimdal.info
/Users/runner/work/heimdal/heimdal/doc/hx509.texi:11: warning: unrecognized encoding name `UTF-8'.
/Users/runner/work/heimdal/heimdal/doc/heimdal.texi:12: warning: unrecognized encoding name `UTF-8'.
/Users/runner/work/heimdal/heimdal/doc//setup.texi:380: Next field of node `Using soft aliases for configuring referrals' not pointed to (perhaps incorrect sectioning?).
/Users/runner/work/heimdal/heimdal/doc//setup.texi:404: This node (Checking the setup) has the bad Prev.
/Users/runner/work/heimdal/heimdal/doc//setup.texi:350: Prev field of node `Using hard aliases for realm migration' not pointed to.
/Users/runner/work/heimdal/heimdal/doc//setup.texi:310: This node (Using namespaces and synthetic principals to keep the database small) has the bad Next.
makeinfo: Removing output file `/Users/runner/work/heimdal/heimdal/doc/heimdal.info' due to errors; use --force to preserve.
make[1]: *** [/Users/runner/work/heimdal/heimdal/doc/heimdal.info] Error 1
```
Instead of triggering scan-build builds on pushes to the `scan-build` branch,
or valgrind builds on pushes to the `valgrind` branch, let's have pushes to
branches matching `scan-build*` and `valgrind*` branch name globs trigger the
corresponding builds.
Do not forget to delete those branches when you're done!
- 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.
