Allow on-demand origin tracking on the msan bot.


git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@222353 91177308-0d34-0410-b5e6-96231b3b80d8
Limit the number of concurrent compilations on the sanitizer bootstrap bot.

Also disable ASan instrumentation on the 3rd stage of the ASan bootstrap.


git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@222356 91177308-0d34-0410-b5e6-96231b3b80d8