I'm using mach for a while now but something which was strange to me is why it always takes an hour for me to build Firefox. Today I have modified a single cpp file and mach also tried to do a full build. Running make -f client.mk instead works perfect and rebuilt Firefox in 2 minutes. Is something broken with mach currently?
"mach build" with no other arguments actually runs "make -f client.mk" to perform the build, so it's surprising that the results would be different: http://hg.mozilla.org/mozilla-central/file/64d6d002e888/python/mozbuild/mozbuild/mach_commands.py#l106
Yeah, I think that something must have also changed on your machine in order for this to have happened. Can you try this again and see if you can repro it by simply changing the same cpp file? Also, which file was it?
Old bug which doesn't seem to apply anymore. Closing as WFM.