Make sure that the shell tests use the same python interpreter as the
rest of the build instead of picking up `python` from the PATH.
It would be nice if we could use the _disallow helper, but that triggers
on invocations that specify python as the scripting language.
Gracefully deal with JSON crashlogs that don't have thread state
available and print an error saying as much: "No thread state (register
information) available".
rdar://83955858
Differential revision: https://reviews.llvm.org/D111341