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/10/lldb/default.nix

@@ -7,8 +7,8 @@
 , which
 , libedit
 , libxml2
-, llvm
-, clang-unwrapped
+, libllvm
+, libclang
 , python3
 , version
 , darwin
@@ -22,19 +22,22 @@ stdenv.mkDerivation (rec {
 
   src = fetch pname "051p5b04y6z3g730rmc2n2v71lipbw7k69riww3a6sl74myfiaq7";
 
-  patches = [ ./procfs.patch ];
+  patches = [
+    ./procfs.patch
+    ./gnu-install-dirs.patch
+  ];
 
-  nativeBuildInputs = [ cmake python3 which swig lit ]
-    ++ lib.optionals enableManpages [ python3.pkgs.sphinx python3.pkgs.recommonmark ];
+  outputs = [ "out" "lib" "dev" ];
+
+  nativeBuildInputs = [
+    cmake python3 which swig lit
+  ] ++ lib.optionals enableManpages [
+    python3.pkgs.sphinx python3.pkgs.recommonmark
+  ];
 
   buildInputs = [
-    ncurses
-    zlib
-    libedit
-    libxml2
-    llvm
-  ]
-  ++ lib.optionals stdenv.isDarwin [
+    ncurses zlib libedit libxml2 libllvm
+  ] ++ lib.optionals stdenv.isDarwin [
     darwin.libobjc
     darwin.apple_sdk.libs.xpc
     darwin.apple_sdk.frameworks.Foundation
@@ -46,8 +49,9 @@ stdenv.mkDerivation (rec {
   hardeningDisable = [ "format" ];
 
   cmakeFlags = [
+    "-DLLDB_INCLUDE_TESTS=${if doCheck then "YES" else "NO"}"
     "-DLLVM_ENABLE_RTTI=OFF"
-    "-DClang_DIR=${clang-unwrapped}/lib/cmake"
+    "-DClang_DIR=${libclang.dev}/lib/cmake"
     "-DLLVM_EXTERNAL_LIT=${lit}/bin/lit"
   ] ++ lib.optionals stdenv.isDarwin [
     "-DLLDB_USE_SYSTEM_DEBUGSERVER=ON"
@@ -57,33 +61,38 @@ stdenv.mkDerivation (rec {
     "-DLLVM_ENABLE_SPHINX=ON"
     "-DSPHINX_OUTPUT_MAN=ON"
     "-DSPHINX_OUTPUT_HTML=OFF"
+  ] ++ 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 = ''
     # Editor support
     # vscode:
     install -D ../tools/lldb-vscode/package.json $out/share/vscode/extensions/llvm-org.lldb-vscode-0.1.0/package.json
     mkdir -p $out/share/vscode/extensions/llvm-org.lldb-vscode-0.1.0/bin
-    ln -s $out/bin/lldb-vscode $out/share/vscode/extensions/llvm-org.lldb-vscode-0.1.0/bin
+    ln -s $out/bin/llvm-vscode $out/share/vscode/extensions/llvm-org.lldb-vscode-0.1.0/bin
   '';
 
   meta = with lib; {
     description = "A next-generation high-performance debugger";
-    homepage = "https://lldb.llvm.org";
-    license = licenses.ncsa;
-    platforms = platforms.all;
+    homepage    = "https://lldb.llvm.org";
+    license     = licenses.ncsa;
+    platforms   = platforms.all;
   };
 } // lib.optionalAttrs enableManpages {
   pname = "lldb-manpages";
 
   buildPhase = ''
-    make docs-lldb-man
+    make docs-man
   '';
 
   propagatedBuildInputs = [];
 
+  # manually install lldb man page
   installPhase = ''
-    # manually install lldb man page
     mkdir -p $out/share/man/man1
     install docs/man/lldb.1 -t $out/share/man/man1/
   '';