[Dexter] Add `-v` to lit dexter substitutions (#158025)
Buildbot cross-project-tests-sie-ubuntu has been flaky after moving to
lldb-dap.
https://lab.llvm.org/buildbot/#/builders/181/builds/27670 - this test
fails for a single run but unfortunately there's not enough output to
diagnose it.
Add `-v` to the substitutions to get as much info as possible out of
failures. Most tests already have -v added manually. If we ever find a
tests needs to specifically run without it we can revert this and add
`-v` manually to tests it's missing from.
