getdeps: support GETDEPS_WGET_ARGS in wget version

[codyohl]

Summary: X-link: https://github.com/facebook/proxygen/pull/495

X-link: https://github.com/facebook/mvfst/pull/337

X-link: https://github.com/facebook/fboss/pull/194

X-link: https://github.com/facebookincubator/zstrong/pull/748

I found it useful to be able to set GETDEPS_WGET_ARGS to change some of the flags to wget while it's in that fetch mode :)

Differential Revision: D56263907

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D56263907