One possible workflow is bazel run +fail_point_test --run_under="/opt/mongodbtoolchain/v5/bin/gdbserver localhost:12345" and then in another terminal /opt/mongodbtoolchain/v5/bin/gdb -ex 'target remote localhost:12345'

That will launch the test with gdbserver attached such that it will pause before starting. Then the other terminal can set breakpoints or just run c (or continue) to run the process

We may want to expose //:gdbserver or at least @gdb_v5//:gdbserver so that it doesn't need to use the installed toolchain