message: Add note on compilationDatabaseDirectory option
  This is useful when building with cmake
diff: @@ -75,7 +75,9 @@ generate one in ninja. When you sync your code you should regenerate this file.
  $ ninja -C out/Release -t compdb cxx cc > compile_commands.json
  ```
  -The `compile_commands.json` file should be in the top-level workspace directory.
  +If the `compile_commands.json` is not in the top-level workspace directory,
  +then the `cquery.misc.compilationDatabaseDirectory` setting can be used to
  +specify its location.
  ### cquery.index.extraClangArguments
  