LTO is disabled during bootstrap to keep the bootstrap tools small and
avoid unnecessary LLVM rebuilds, but is enabled in the final stdenv
stage and should be usable by normal packages.
Since years I'm not maintaining anything of the list below other
than some updates when I needed them for some reason. Other people
is doing that maintenance on my behalf so I better take me out but
for very few packages. Finally!
Previously we only set these when using musl.
See https://github.com/NixOS/nixpkgs/pull/42452#discussion_r197618464
Same should be done for changes in #42452,
I'll add a follow-up commit doing so in the PR containing this
or wherever makes sense-- depending on how review/merging of that goes.
Sending similar changes for LLVM 4 to master, as suggested.
We already did them on non-mass-rebuild llvm 6. Also, this allows
simplifying the stdenv booting.
We were missing the libcxxabi dep in compile-rt in llvm 6, so fixed that
too.
This requires some small changes in the stdenv, then working around the
weird choice LLVM made to hardcode @rpath in its install name, and then
lets us remove a ton of annoying workaround hacks in many of our Go
packages. With any luck this will mean less hackery going forward.
