This build re-uses the PGO profile from the win64 build in the
win64-aarch64-shippable-no-eme part of the aarch64 build. Even though
the profile isn't generated on the smae platform, we still get enough of
a performance win to make this worthwhile.
Note that the pgo_flags() in configure need to be tweaked slightly since
we don't supprt the -fprofile-generate flag for aarch64 (we don't build
the clang_rt.profile lib there). So we always want to return the flags
namespace to make sure we get the use_* versions of flags, which we do
need.
Differential Revision: https://phabricator.services.mozilla.com/D38928
--HG--
extra : moz-landing-system : lando
98ffc560c9