Happens with some frequency with building Gecko. You can see documented instances of it for the CLOBBER file. It allows the person building to optionally have t

Happens with some frequency with building Gecko. You can see documented instances of it for the CLOBBER file. It allows the person building to optionally have the build system force a clean rebuild. https://hg.mozilla.org/mozilla-central/log/tip/CLOBBER https://hg.mozilla.org/mozilla-central/log/tip/CLOBBER https://firefox-source-docs.mozilla.org/build/buildsystem/mozconfigs.html#mk-add-options https://firefox-source-docs.mozilla.org/build/buildsystem/mo...