message: Allow LLDB to find sources.
  Summary: Tell LLDB to prefix source paths with the `debug-source-root`
diff: @@ -86,8 +86,11 @@ def dbg_prefix(dbg, src_root=None):
  assert dbg in ["gdb", "lldb"]
  cmd = [dbg]
  - if dbg == "gdb" and src_root is not None:
  + if src_root is not None:
  + if dbg == "gdb":
  cmd += ["-ex", quote("directory %s" % src_root)]
  + elif dbg == "lldb":
  + cmd += ["-o", quote('settings set target.source-map "." "%s"' % src_root)]
  DBG_END = {"gdb": "--args", "lldb": "--"}
  cmd.append(DBG_END[dbg])
  