To provide a more "high level" view of progress, don't output build logs
of each componets on stdout, but write them in files in the logs/ directory.

This idea was suggested by mcs and Kathy in this comment:
https://trac.torproject.org/projects/tor/ticket/17379#comment:12

Update rbm and add example rbm.local.conf file.

- Fix docker_remote_finish for docker >= 1.10.0
- If the TMPDIR env var exists, use it instead of /tmp

David Fifield authored Jan 23, 2017 and boklm committed Feb 09, 2017

https://lists.torproject.org/pipermail/tor-project/2017-January/000906.html

Kathleen Brade authored Jan 26, 2017 and boklm committed Feb 09, 2017

Adjust the comments to account for recent Torbutton changes.

We need the 10.7 SDK to build GO.

Kathleen Brade authored Jan 17, 2017 and boklm committed Jan 30, 2017

Allow full read access to all files under /usr/lib.
Allow full read access to /Library/Preferences/com.apple.ViewBridge.plist.
Allow writes to TorBrowser-Data/Browser/profiles.ini (otherwise, a new
  browser profile is created each time the browser is opened).

macosx-toolchain is currently used in two components: firefox and tor.
In the firefox build we don't use those (unexported) variables. In the
tor build we only use CFLAGS and CXXFLAGS through the configure options,
and we move them to var/FLAGS in rbm.conf.

Add target to remove the subdirectory including the version number (or
date) from the output directory. The output directory can be selected
with the --output-dir option.