1456900 - Get the PROFILE_GEN_CFLAGS workaround out of memory/build/Makefile.in

Status: NEW

(Firefox Build System :: General, enhancement)

Description

[(not currently active) Ted Mielczarek]

bug 1413570 added a workaround for issues building mozjemalloc with PGO:
https://hg.mozilla.org/mozilla-central/file/dfb15917c057f17e5143f7d7c6e1972ba53efc49/memory/build/Makefile.in#l8

We should figure out how to get this into moz.build. Currently the whole `COMPILE_FLAGS` setup is ignorant of `PROFILE_{GEN,USE}_CFLAGS`, they get selected in config.mk:
https://dxr.mozilla.org/mozilla-central/rev/26e53729a10976f52e75efa44e17b5e054969fec/config/config.mk#154

What's more, that code also handles per-file disabling of PGO, which is pretty awful.

Long-term we probably want to split PGO builds into two completely separate builds as we've discussed in the past, but maybe we can come up with a shorter-term mitigation here.