When arc is run with --trace, print out argv explicitly

Summary:
Ref T9993. Users may have shell aliases or wrapper scripts that they forget about.

Print out the arguments we received to make it obvious that something went through an indirection layer.

Test Plan: Ran arc version --help.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9993

Differential Revision: https://secure.phabricator.com/D14797