Build System Project - Latest Update

[David Burns]

Below is a highlight of all work the build peers have done since the last
report[1].

The build peers have been working to get faster builds in automation as
well as for local developers. We have landed changes to stop generating
XPIDL sources in artifact builds[2], which is a performance and correctness
improvement.

We have also been working hard at removing the legacy m4+shell autoconf
mess. We are now below 70% of the size when we started this project. Since
the last update we have removed over 3000 lines[3].

Build tasks in taskcluster are now using c4.4xlarge instances instead of
c3.2xlarge[4] - builds are faster by around 20%[5].

As part of the work to allow us to use an alternate build backend we have
managed to get Firefox building NSS with GYP on Linux[6]. Other platforms
are to follow before we land this change. We have also been reviewing
changes to build XPIDL sources with TUP[7].

Support for building Rust sources via Cargo has been landed in
mozilla-central[8]. For more information read the Dev.Platform post[9]

Last but not least, our intern project to use msys2 has reached its goal.
The new msys2 environment now builds on mozilla-central. We will be sending
out a separate email about this for those who would like to try it out.

[1]
https://groups.google.com/d/msg/mozilla.dev.platform/i0rRsYgnXDM/O5DxU-PqBQAJ

[2] https://bugzilla.mozilla.org/show_bug.cgi?id=1240134

[3] https://bugzilla.mozilla.org/show_bug.cgi?id=1292463

[4] https://bugzilla.mozilla.org/show_bug.cgi?id=1290282

[5] https://mzl.la/2c5bjSR

[6] https://bugzilla.mozilla.org/show_bug.cgi?id=1237872

[7] https://bugzilla.mozilla.org/show_bug.cgi?id=1293448

[8] https://bugzilla.mozilla.org/show_bug.cgi?id=1231764

[9]
https://groups.google.com/d/msg/mozilla.dev.platform/ZgkBLZb6dtc/oWBE_nUxAQAJ