[Dexter] Temporarily print DAP logs on specific exception (#157130)
Buildbot cross-project-tests-sie-ubuntu sees sporadic test failures due to
missing "stackTrace" "source" "path". The "path" field is optional for
"source" according to DAP, so it's well formed. It works most of the time,
and doesn't consistently fail for any one test which is all strangely
inconsistent.
The failures couldn't be reproduced locally after running the feature_tests
in a loop for 3 hours. I haven't been able to work out why the "source" is
sometimes missing by just looking at LLDB code.
This patch prints the DAP log to stderr when the specific error condition is
hit, to help us understand why LLDB is sometimes getting into this state.
Dump additional context from FileCheck so this can be seen on the bots (on
a failure).
This patch will be reverted once we've collected some logs.