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
  db29857eb3, 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)`

pkgs/development/compilers/llvm/6/lldb/default.nix

@@ -8,14 +8,14 @@
 , which
 , libedit
 , libxml2
-, llvm
-, clang-unwrapped
+, libllvm
+, libclang
 , python3
 , version
 , darwin
 }:
 
-stdenv.mkDerivation {
+stdenv.mkDerivation rec {
   pname = "lldb";
   inherit version;
 
@@ -28,29 +28,46 @@ stdenv.mkDerivation {
       sha256 = "1zbx4m0m8kbg0wq6740jcw151vb2pb1p25p401wiq8diqqagkjps";
       stripLen = 1;
     })
+    ./gnu-install-dirs.patch
   ];
 
   postPatch = ''
     # Fix up various paths that assume llvm and clang are installed in the same place
-    sed -i 's,".*ClangConfig.cmake","${clang-unwrapped}/lib/cmake/clang/ClangConfig.cmake",' \
+    sed -i 's,".*ClangConfig.cmake","${libclang.dev}/lib/cmake/clang/ClangConfig.cmake",' \
       cmake/modules/LLDBStandalone.cmake
-    sed -i 's,".*tools/clang/include","${clang-unwrapped}/include",' \
+    sed -i 's,".*tools/clang/include","${libclang.dev}/include",' \
       cmake/modules/LLDBStandalone.cmake
-    sed -i 's,"$.LLVM_LIBRARY_DIR.",${llvm}/lib ${clang-unwrapped}/lib,' \
+    sed -i 's,"$.LLVM_LIBRARY_DIR.",${libllvm.lib}/lib ${libclang.lib}/lib,' \
       cmake/modules/LLDBStandalone.cmake
   '';
 
-  nativeBuildInputs = [ cmake python3 which swig ];
-  buildInputs = [ ncurses zlib libedit libxml2 llvm ]
-    ++ lib.optionals stdenv.isDarwin [ darwin.libobjc darwin.apple_sdk.libs.xpc darwin.apple_sdk.frameworks.Foundation darwin.bootstrap_cmds darwin.apple_sdk.frameworks.Carbon darwin.apple_sdk.frameworks.Cocoa ];
+  outputs = [ "out" "lib" "dev" ];
+
+  nativeBuildInputs = [
+    cmake python3 which swig
+  ];
+
+  buildInputs = [
+    ncurses zlib libedit libxml2 libllvm
+  ] ++ lib.optionals stdenv.isDarwin [
+    darwin.libobjc
+    darwin.apple_sdk.libs.xpc
+    darwin.apple_sdk.frameworks.Foundation darwin.bootstrap_cmds darwin.apple_sdk.frameworks.Carbon darwin.apple_sdk.frameworks.Cocoa
+  ];
 
   CXXFLAGS = "-fno-rtti";
   hardeningDisable = [ "format" ];
 
   cmakeFlags = [
+    "-DLLDB_INCLUDE_TESTS=${if doCheck then "YES" else "NO"}"
     "-DLLDB_CODESIGN_IDENTITY=" # codesigning makes nondeterministic
+  ] ++ lib.optionals doCheck [
+    "-DLLDB_TEST_C_COMPILER=${stdenv.cc}/bin/${stdenv.cc.targetPrefix}cc"
+    "-DLLDB_TEST_CXX_COMPILER=${stdenv.cc}/bin/${stdenv.cc.targetPrefix}c++"
   ];
 
+  doCheck = false;
+
   postInstall = ''
     mkdir -p $out/share/man/man1
     cp ../docs/lldb.1 $out/share/man/man1/