Right now this runs during the `maybe_clobber_profilebuild` step in the root Makefile.in. Merging the profile needs to happen in the second stage of the new PGO scheme so it would be more convenient to do this somewhere else, either as a part of a mozharness script or profileserver.py.

Note that we do currently use profileserver.py in the valgrind builds (just to have a fairly small test that actually runs Firefox).

Nevermind, I was wrong, we use mozrunner directly in the valgrind-test command: https://dxr.mozilla.org/mozilla-central/rev/b0b856065d5b7ad2996f707e6e797d0d72afd803/build/valgrind/mach_commands.py#46

Per bug 1507346 comment 2 we'll probably need to do this in the final build step since the tools we use are host binaries, so they won't run on macos, for example.

Also on Windows the re-build will need cygprofile.txt from the profiling step.

Pushed by cmanchester@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/3b1c7ad601ba Add configure machinery for MOZ_PROFILE_USE and merging profile. r=nalexander https://hg.mozilla.org/integration/autoland/rev/df23b1fa16f5 Add a configure option for JARLOG_FILE in profile use builds. r=nalexander

https://hg.mozilla.org/mozilla-central/rev/3b1c7ad601ba https://hg.mozilla.org/mozilla-central/rev/df23b1fa16f5