This is in an effort to fix the following build failure shown by
chromium:
clang++: error: no such file or directory: '/nix/store/fhd89wrmkx6nflzjk0d6waz70bk3zc4i-clang-wrapper-12.0.0/resource-root/share/cfi_blacklist.txt'
As it turns out a change introduced via the gnu-install-dirs.patch
caused `add_compiler_rt_resource_file` to install resource files to
$dev/include (FULL_INCLUDEDIR) instead of $out/share (FULL_DATADIR)
which in turn meant that the clang wrappers we had didn't link those
files to its resource root at all.
Alternative fix to this would have been to link
compiler-rt.dev/include/*.txt to the wrappers resource-root/share as
well, but since this was handled inconsistently across the patch anyways
(the dfsan list is installed correctly), opt to handle this
consistently within the patch.
llvmPackages_{5,6} install the resource files to a completely different
location and need separate investigation.
Also begin to start work on cross compilation, though that will have to
be finished later.
The patches are based on the first version of
https://reviews.llvm.org/D99484. It's very annoying to do the
back-porting but the review has uncovered nothing super major so I'm
fine sticking with what I've got.
Beyond making the outputs work, I also strove to re-sync the packages,
as they have been drifting pointlessly apart for some time.
----
Other misc notes, highly incomplete
- lvm-config-native and llvm-config are put in `dev` because they are
tools just for build time.
- Clang no longer has an lld dep. That was introduced in
db29857eb391ed002046090851a44c452b80bdbd, but if clang needs help
finding lld when it is used we should just pass it flags / put in the
resource dir. Providing it at build time increases critical path
length for no good reason.
----
A note on `nativeCC`:
`stdenv` takes tools from the previous stage, so:
1. `pkgsBuildBuild`: `(?1, x, x)`
2. `pkgsBuildBuild.stdenv.cc`: `(?0, ?1, x)`
while:
1. `pkgsBuildBuild`: `(?1, x, x)`
2. `pkgsBuildBuild.targetPackages`: `(x, x, ?2)`
3. `pkgsBuildBuild.targetPackages.stdenv.cc`: `(?1, x, x)`
