APT source whitelist request for ppa:team-gcc-arm-embedded/ppa

[ppannuto]

This is the official PPA for the arm compiler, supported and maintained by ARM.

There are 3 old issues requesting cross-compiler PPAs, but they all point to older/non-official PPAs and the most recent is from late 2015. They are #34 #41 and #132.

There are 2 old pull requests, #334 was opened and closed by its author. #219 is still open and effectively requests the same package, however the README for this repo clearly requests issues, thus this issue.

[offa]

In the meantime it's possible to add the ppa through a sourceline.