globally installed bzlgen uses install dir as base_dir, not run directory

[mattem]

bzlgen can be installed globally, currently by running bazel run //:pkg.pack and npm i -g on the resulting tar. However bzlgen will use the install dir as base_dir, not the directory in which it's currently running.

This can be currently worked around by passing --base_dir $(pwd) as a flag.

matt@Matts-MacBook-Pro $ bzlgen sass libs/components/src/playout/mini-playlist/_mini-playlist.common.scss
ℹ  info      Generating BUILD file with type 'sass' for 'libs/components/src/playout/mini-playlist/_mini-playlist.common.scss'
✖  error     The workspace at /Users/matt/.nvm/versions/node/v10.15.3/lib/node_modules/@evertz/bzlgen does not appear to be a bazel workspace. Missing root BUILD file