Remove unnecessary allocation, update API name for starting the rustc dr...

[bjadamson]

Removes an unnecessary allocation when passing the command line arguments to the librustc driver.

[alexcrichton]

Oh dear, looks like this picked up some extra commits! @bjadamson, could you rebase those out of this PR?

[bjadamson]

Hey Alex, sorry never done this before (I know how to rebase, but the guide I found for rebasing a pull request assumes I have push permissions: https://github.com/edx/edx-platform/wiki/How-to-Rebase-a-Pull-Request )

The commit looks correct on my end (in my fork)
https://github.com/bjadamson/rust/commit/d96faf7e7178f211148e2abcdb3282579817364e

I'm sure there's something obvious I'm missing (we don't get to use GitHub at work :( )

[alexcrichton]

No problem! These commands should help out:

git checkout -b tmp 
git reset --hard fd6ec2d # your commit on this branch
git fetch origin # whatever the mozilla remote is called
git rebase origin/master # do the rebase
git push bjadamson tmp:rustc-improvements -f # force-push this branch

[bjadamson]

Ok I think it's good! I think the key concept here was that I could automatically update this pull request just by pushing to my forked repo again. Thanks!