Support |ac_add_options --enable-artifact-builds| / build mode which doesn't require compiling and linking for changes in static files (JS,HTML,XML,XUL). Unchanged artifacts should be downloaded from a server. Bug 901840 added this for Firefox. Comparison on a Windows machine for a Firefox build after clobber: without artifact mode: >42 minutes with artifact mode: <3 minutes And |mach build faster| after that takes only 6 seconds.
a year ago
See bug 1279781 for a previous attempt to get mach build faster going. Bug 901840 has a lot of dependencies. Do you happen to have a tl;dr version of what needs to be changed in Thunderbird?