tree 53d669f94a94d21d6207e283730bcf49b66b7647
parent df9c4caad84d1a06094aefba04846ae895a7f124
author Ian McKellar <ianloic@google.com> 1539628955 -0700
committer Ian McKellar <ianloic@google.com> 1543861796 -0800

[fx] validate `fx use` arg

Now `fx use` will check that there exists an `args.gn` in the directory
indicated.

Change-Id: I96194fdf2040d2c0cfa81c9d62256f596d3a090f