Revert "[sanitizer] Move definition of stable-runtime to common lit config."

This reverts commit r245263, and the change wasn't catched by UBsan.

It also reverts: "[ARM] Also disable stable-runtime check on UBsan,
to use generic one" (r245287), as it didn't fix the UBsan builds.

We need to investigate what's going on before continuing, since this
is breaking all ARM RT buildbots for a while.

llvm-svn: 245292