Per BoringSSL's FIPS policy, its `main` branch is the "update branch"
for FedRAMP compliance's purposes.
This means that we can stop using a specific BoringSSL branch when
enabling FIPS, as well as a number of hacks that allowed us to build
more recent BoringSSL versions with an older pre-compiled FIPS modules.
This also required slightly updating the main BoringSSL submodule, as
the previous version had an issue when building with the FIPS option
enabled. This is turn required some changes to the PQ patch as well as
some APIs that don't seem to be exposed publicly, as well as changing
some paths in the other patches.
In order to allow a smooth upgrade of internal projects, the `fips-compat`
feature is reduced in scope and renamed to `legacy-compat-deprecated` so
that we can incrementally upgrade internal BoringSSL forks. In practice
this shouldn't really be something anyone else would need, since in
order to work it requires a specific mix of BoringSSL version and
backported patches.
This adds a feature to build against a BoringSSL version compatible with
the current boringssl-fips, but _without_ actually enabling the `fips`
feature.
This can be useful to use with `fips-link-precompiled` while using a
custom BoringSSL version based on the older FIPS branch.
This feature expects a recent boringssl checkout (such as the one
found in boring-sys/deps/boringssl), so it should not be using
the same bindings as the fips feature, which are based on
boring-sys/deps/boringssl-fips, which is older and with a different
API.
Alessandro Ghedini