llvmPackages: Multuple outputs for everythting

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)`

1 files changed, 2 insertions, 2 deletions

diff --git a/pkgs/applications/editors/jucipp/default.nix b/pkgs/applications/editors/jucipp/default.nix
index 7304219e23693..140bf04c9f365 100644
--- a/pkgs/applications/editors/jucipp/default.nix
+++ b/pkgs/applications/editors/jucipp/default.nix
@@ -56,8 +56,8 @@ stdenv.mkDerivation rec {
     e = "\");";
     v = lib.getVersion llvmPackages.clang;
   in
-    p+llvmPackages.libcxx+"/include/c++/v1"+e
-    +p+llvmPackages.clang-unwrapped+"/lib/clang/"+v+"/include/"+e
+    p+llvmPackages.libcxx.dev+"/include/c++/v1"+e
+    +p+llvmPackages.clang-unwrapped.lib+"/lib/clang/"+v+"/include/"+e
     +p+glibc.dev+"/include"+e;
 
   preConfigure = ''