With bug 643704, we added support for a mozconfig option to trigger PGO builds. This also means that the converse, disabling PGO, is also possible through mozconfig... but not while buildbots call the profiledbuild target of client.mk. The build target should be called like on other non PGO builds, and the following added to windows mozconfigs: mk_add_options MOZ_PGO=1 This has only landed on m-c so far, but we'll likely want to get this on stable branches as well.

Is it possible to have profiledbuild be a no-op target that depends on build until this is landed on all stable branches? something like .PHONY: profiledbuild profiledbuild: build @echo using make -f client.mk profiledbuild is deprecated

The profiledbuild target is still used to to the actual work. The build target either calls profiledbuild or realbuild depending on that MOZ_PGO variable. And profiledbuild calls realbuild twice.

This is a very small subset of the work happening in bug 658313