Build System Project - Latest Update

[David Burns]

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

We have reduced the time it takes to run reftests as well as the amount of
I/O that happens during the tests by disabling some features in Firefox
that are not used during the test. This has saved over 50GB of I/O in
automation. Reporting has been put in place to help monitor in automation
to help us spot issues like this in the future! We have hopefully spotted a
few and will hopefully comment in the next update.

The build peers have also been working hard on getting a distributed cache
ready for everyone to use. This means we will try get get from the globally
distributed cache before building, hopefully saving time by only building
things that have changed and the cache for everything else.

We are continuing our work to remove configure/m4 code and have removed
around 2000 lines[2] as well as working our way through the long tail of
MakeFiles. We are down to just over 100 files and few thousand lines of
code.[3]. Once we have completed enough of this work we can start looking
to move over to a more performant build backend.

Last, but not least, I want to introduce our intern for the Summer, Nathan
Hakkakzadeh [Nat on IRC]. He will be helping with various Windows build
tasks while working with us. Make sure to say Hi to him!

[1]
https://groups.google.com/d/msg/mozilla.dev.platform/aQVrp8GElno/QbGac4drAQAJ

[2] https://plot.ly/~glandium/14/lines-vs-time/

[3] http://people.mozilla.org/~tmielczarek/makefiles/makefiles_count.html