Don't know if this is all: http://hg.mozilla.org/mozilla-central/annotate/3094601af679/toolkit/content/Makefile.in#l29 or something else as well. I couldn't find anything calling sethostname in our tree from a cursory glance, and yet I see this every build, so...
This is only used for about:buildconfig: https://dxr.mozilla.org/mozilla-central/source/toolkit/content/buildconfig.html#23 so we could make this ifdef MOZILLA_OFFICIAL or something like that.
Or... we could stop putting that on about:buildconfig. Seriously, what does that buy us to know what builder did the build, from Firefox itself? We can figure that out from buildbot itself if we really need that info.
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