LLVM 11 libcxxabi has some flags to support usage in the Darwin stdenv,
in particular, `standalone` and `withLibunwind`.
Darwin stdenv needs the `standalone` flag because its `hostPlatform` set
doesn't have `useLLVM` set to true. And it needs `withLibunwind` to
explicitly disable including `libunwind` as a build input.
We also prefix `install_name_tool` in case we're cross-compiling.
This is already done for previous versions of clang which use
a release tarball, but must be done differently for the more
recent versions which use fetchFromGitHub.
Fixes clang-tools clangd wrapper
Commit 199b7c50 "compiler-rt: remove <cyclades.h> from libsanitizer"
broke conditional conditional musl patches.
The change has a few effects:
- pkgsStatic.llvmPackages_{5,6,7}.compiler-rt: fix build on musl after cyclades backport
- pkgsStatic.llvmPackages_{{5..13},git}.compiler-rt: drop incomplete musl patches as
sanitizers are disabled anyway and require more upstream porting.
the fix to extendDerivation in #140051 unwittingly worsened eval performance by
quite a bit. set elements alone needed over 1GB extra after the change, which
seems disproportionate to how small it was. if we flip the logic used to
determine which outputs to install around and keep a "this one exactly" flag in
the specific outputs instead of a "all of them" in the root we can avoid most
of that cost.
To avoid unnecessary builds but this needs to be fixed ASAP. Chromium
already depends on it and a lot of additional packages, including Mesa,
will depend on it after the stable release.
