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, 1 insertions, 1 deletions

diff --git a/pkgs/development/libraries/qt-4.x/4.8/default.nix b/pkgs/development/libraries/qt-4.x/4.8/default.nix
index a4ac41d81df76..532a72c820ce0 100644
--- a/pkgs/development/libraries/qt-4.x/4.8/default.nix
+++ b/pkgs/development/libraries/qt-4.x/4.8/default.nix
@@ -204,7 +204,7 @@ stdenv.mkDerivation rec {
     ++ lib.optional stdenv.isLinux "-std=gnu++98" # gnu++ in (Obj)C flags is no good on Darwin
     ++ lib.optionals (stdenv.isFreeBSD || stdenv.isDarwin)
       [ "-I${glib.dev}/include/glib-2.0" "-I${glib.out}/lib/glib-2.0/include" ]
-    ++ lib.optional stdenv.isDarwin "-I${libcxx}/include/c++/v1");
+    ++ lib.optional stdenv.isDarwin "-I${lib.getDev libcxx}/include/c++/v1");
 
   NIX_LDFLAGS = lib.optionalString (stdenv.isFreeBSD || stdenv.isDarwin) "-lglib-2.0";