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/12/lldb/default.nix

@@ -1,4 +1,5 @@
 { lib, stdenv, llvm_meta
+, runCommand
 , fetch
 , cmake
 , zlib
@@ -7,8 +8,8 @@
 , which
 , libedit
 , libxml2
-, llvm
-, clang-unwrapped
+, libllvm
+, libclang
 , python3
 , version
 , libobjc
@@ -27,17 +28,30 @@ stdenv.mkDerivation (rec {
 
   src = fetch pname "1v85qyq3snk81vjmwq5q7xikyyqsfpqy2c4qmr81mps4avsw1g0l";
 
-  patches = [ ./lldb-procfs.patch ];
+  patches = [
+    ./procfs.patch
+    (runCommand "resource-dir.patch" {
+      clangLibDir = "${libclang.lib}/lib";
+    } ''
+      substitute '${./resource-dir.patch}' "$out" --subst-var clangLibDir
+    '')
+    ./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
+    libllvm
   ]
   ++ lib.optionals stdenv.isDarwin [
     libobjc
@@ -51,8 +65,9 @@ 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"
@@ -62,8 +77,13 @@ 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:
@@ -90,6 +110,7 @@ stdenv.mkDerivation (rec {
   '';
 
   propagatedBuildInputs = [];
+
   # manually install lldb man page
   installPhase = ''
     mkdir -p $out/share/man/man1

pkgs/development/compilers/llvm/12/lldb/gnu-install-dirs.patch

@@ -0,0 +1,65 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index b5633e21c56a..f2f1035e9238 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -10,6 +10,8 @@ set(CMAKE_MODULE_PATH
+ # If we are not building as part of LLVM, build LLDB as a standalone project,
+ # using LLVM as an external library.
+ if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
++  include(GNUInstallDirs)
++
+   project(lldb)
+   include(LLDBStandalone)
+ 
+diff --git a/cmake/modules/AddLLDB.cmake b/cmake/modules/AddLLDB.cmake
+index 4ed5c647c5d2..89f96e710d55 100644
+--- a/cmake/modules/AddLLDB.cmake
++++ b/cmake/modules/AddLLDB.cmake
+@@ -107,13 +107,13 @@ function(add_lldb_library name)
+   endif()
+ 
+   if(PARAM_SHARED)
+-    set(install_dest lib${LLVM_LIBDIR_SUFFIX})
++    set(install_dest ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX})
+     if(PARAM_INSTALL_PREFIX)
+       set(install_dest ${PARAM_INSTALL_PREFIX})
+     endif()
+     # RUNTIME is relevant for DLL platforms, FRAMEWORK for macOS
+     install(TARGETS ${name} COMPONENT ${name}
+-      RUNTIME DESTINATION bin
++      RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+       LIBRARY DESTINATION ${install_dest}
+       ARCHIVE DESTINATION ${install_dest}
+       FRAMEWORK DESTINATION ${install_dest})
+diff --git a/cmake/modules/LLDBConfig.cmake b/cmake/modules/LLDBConfig.cmake
+index 2fdf1502d055..37364341ff8b 100644
+--- a/cmake/modules/LLDBConfig.cmake
++++ b/cmake/modules/LLDBConfig.cmake
+@@ -225,7 +225,7 @@ include_directories(BEFORE
+ if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
+   install(DIRECTORY include/
+     COMPONENT lldb-headers
+-    DESTINATION include
++    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+     FILES_MATCHING
+     PATTERN "*.h"
+     PATTERN ".cmake" EXCLUDE
+@@ -233,7 +233,7 @@ if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
+ 
+   install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/include/
+     COMPONENT lldb-headers
+-    DESTINATION include
++    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+     FILES_MATCHING
+     PATTERN "*.h"
+     PATTERN ".cmake" EXCLUDE
+diff --git a/tools/intel-features/CMakeLists.txt b/tools/intel-features/CMakeLists.txt
+index 734167e51bc5..f95761b5df58 100644
+--- a/tools/intel-features/CMakeLists.txt
++++ b/tools/intel-features/CMakeLists.txt
+@@ -65,4 +65,4 @@ if (LLDB_ENABLE_PYTHON AND LLDB_BUILD_INTEL_PT)
+ endif()
+ 
+ install(TARGETS lldbIntelFeatures
+-  LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX})
++  LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX})

pkgs/development/compilers/llvm/12/lldb/resource-dir.patch

@@ -0,0 +1,13 @@
+diff --git a/lldb/cmake/modules/LLDBConfig.cmake b/lldb/cmake/modules/LLDBConfig.cmake
+index 37364341ff8b..7f74c1a3e257 100644
+--- a/cmake/modules/LLDBConfig.cmake
++++ b/cmake/modules/LLDBConfig.cmake
+@@ -257,7 +257,7 @@ if (NOT TARGET clang-resource-headers)
+   # Iterate over the possible places where the external resource directory
+   # could be and pick the first that exists.
+   foreach(CANDIDATE "${Clang_DIR}/../.." "${LLVM_DIR}" "${LLVM_LIBRARY_DIRS}"
+-                    "${LLVM_BUILD_LIBRARY_DIR}"
++                    "${LLVM_BUILD_LIBRARY_DIR}" "@clangLibDir@"
+                     "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}")
+     # Build the resource directory path by appending 'clang/<version number>'.
+     set(CANDIDATE_RESOURCE_DIR "${CANDIDATE}/clang/${LLDB_CLANG_RESOURCE_DIR_NAME}")