If the default target and host triple don't match then print the following
message when the lit test runs:
Forcing dexter tests to use host triple {HOST_TRIPLE}.
If we can't target the host arch then, when lit runs, we mark
the dexter test directories as UNSUPPORTED and print the message:
Host triple {HOST_TRIPLE} not supported. Skipping dexter tests in
the debuginfo-tests project.
Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D96494