TODO list for this and next week

1. ✔ Fix up the rhub R package, make it public.
2. ✔ Provide proper sanitizer output from the SAN image
3. ✔ More Windows versions: R-devel, R-release, R-patched.
4. ✔ Create a proper Windows builder image
5. ✔ Nice output in emails
6. ✔ Build time limit
7. ✔ Passing arguments to the build command, e.g. --valgrind
8. ✔ Think about sysreqs on Windows
9. ✔ Think about caching binaries for Linux