Fix how we set 'build_dir' and 'install_dir' options from 'install' options -- irrelevant because this file is about to go away, but oh well.
Fix how we set 'build_dir' and 'install_dir' options from 'install' options --
irrelevant because this file is about to go away, but oh well.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator