[lldb][test] Use a fake dsymForUUID in tests (#201547)
Our test should not invoke dsymForUUID as it creates an unnecessary
dependency on the OS and is also incredibly slow. For example, all
Crashlog tests on my system run for more than 30s and all of this is
just spent waiting for dsymForUUID to return "not found".
This patch provides a simple dummy dsymForUUID script we set for all
tests. This is automatically picked up by LLDB with the existing
dsymForUUID environment variable. As a result, all crashlog tests which
previously run in total for about 4 minutes with one job, now run in
about 10s.
assisted-by: claude
