[cmake] Pass external project source directories to sub-configures

[smeenai]

Summary

We're passing LLVM_EXTERNAL_PROJECTS to cross-compilation configures, so
we also need to pass the source directories of those projects, otherwise
configuration can fail from not finding them.

[compnerd]

I’m not sure that this is the best direction long term. This is specific to the LLVM build, the runtimes builds do not take these parameters, and they are the primary things we’re trying to cross compile with this infrastructure. But the monorepo makes this more complicated and makes the configure the same, so, yes, I suppose this needs to be preserved. *sigh*

[smeenai]

In D69076#1713418, @compnerd wrote:

I’m not sure that this is the best direction long term. This is specific to the LLVM build, the runtimes builds do not take these parameters, and they are the primary things we’re trying to cross compile with this infrastructure. But the monorepo makes this more complicated and makes the configure the same, so, yes, I suppose this needs to be preserved. *sigh*

I believe the runtimes builds use the ExternalProject infrastructure. The CrossCompile infrastructure is used for e.g. building native tablegen binaries when you're cross-compiling LLVM.

[aprantl]

Either this or https://reviews.llvm.org/D69031 broke the lldb-cmake bot: http://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/2706/

Script:
--
: 'RUN: at line 4';   /Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/bin/clang --driver-mode=cl -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk -fmodules-cache-path=/Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/tools/lldb/lldb-test-build.noindex/module-cache-clang/lldb-shell --target=i386-windows-msvc -Od -Z7 -c /Fo/Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/tools/lldb/test/SymbolFile/NativePDB/Output/function-types-calling-conv.cpp.tmp.obj -- /Users/buildslave/jenkins/workspace/lldb-cmake/llvm-project/lldb/test/Shell/SymbolFile/NativePDB/function-types-calling-conv.cpp
: 'RUN: at line 5';   /Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/bin/lld-link -debug:full -nodefaultlib -entry:main /Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/tools/lldb/test/SymbolFile/NativePDB/Output/function-types-calling-conv.cpp.tmp.obj -out:/Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/tools/lldb/test/SymbolFile/NativePDB/Output/function-types-calling-conv.cpp.tmp.exe -pdb:/Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/tools/lldb/test/SymbolFile/NativePDB/Output/function-types-calling-conv.cpp.tmp.pdb
: 'RUN: at line 6';   env LLDB_USE_NATIVE_PDB_READER=1 /Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/bin/lldb --no-lldbinit -S /Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/tools/lldb/test/Shell/lit-lldb-init -f /Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/tools/lldb/test/SymbolFile/NativePDB/Output/function-types-calling-conv.cpp.tmp.exe -s      /Users/buildslave/jenkins/workspace/lldb-cmake/llvm-project/lldb/test/Shell/SymbolFile/NativePDB/Inputs/function-types-calling-conv.lldbinit | /Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/bin/FileCheck /Users/buildslave/jenkins/workspace/lldb-cmake/llvm-project/lldb/test/Shell/SymbolFile/NativePDB/function-types-calling-conv.cpp
--
Exit Code: 1

Command Output (stderr):
--
clang-10: warning: unknown argument ignored in clang-cl: '-isysroot' [-Wunknown-argument]
clang-10: warning: unknown argument ignored in clang-cl: '-fmodules-cache-path=/Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/tools/lldb/lldb-test-build.noindex/module-cache-clang/lldb-shell' [-Wunknown-argument]
clang-10: error: cannot specify '/Fo/Users/buildslave/jenkins/workspace/lldb-cmake/lldb-build/tools/lldb/test/SymbolFile/NativePDB/Output/function-types-calling-conv.cpp.tmp.obj' when compiling multiple source files
clang-10: warning: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk: 'linker' input unused [-Wunused-command-line-argument]

[aprantl]

If I had to guess it's probably https://reviews.llvm.org/D69031.

[smeenai]

I think that's unrelated? The other diff got reverted and the build seems to be happy now.

llvm/cmake/modules/CrossCompile.cmake

+include(AddLLVM)
 include(LLVMExternalProjectUtils)
 
 
 function(llvm_create_cross_target project_name target_name toolchain buildtype)
 
   if(NOT DEFINED ${project_name}_${target_name}_BUILD)
     set(${project_name}_${target_name}_BUILD
       "${CMAKE_BINARY_DIR}/${target_name}")
function(llvm_create_cross_target project_name target_name toolchain buildtype)
   string(REPLACE ";" "$<SEMICOLON>" experimental_targets_to_build_arg
          "${LLVM_EXPERIMENTAL_TARGETS_TO_BUILD}")
 
   string(REPLACE ";" "$<SEMICOLON>" llvm_enable_projects_arg
          "${LLVM_ENABLE_PROJECTS}")
   string(REPLACE ";" "$<SEMICOLON>" llvm_external_projects_arg
          "${LLVM_EXTERNAL_PROJECTS}")
 
+  set(external_project_source_dirs)
+  foreach(project ${LLVM_EXTERNAL_PROJECTS})
+    canonicalize_tool_name(${project} name)
+    list(APPEND external_project_source_dirs
+         "-DLLVM_EXTERNAL_${name}_SOURCE_DIR=${LLVM_EXTERNAL_${name}_SOURCE_DIR}")
+  endforeach()
+
   add_custom_command(OUTPUT ${${project_name}_${target_name}_BUILD}/CMakeCache.txt
     COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}"
         -DCMAKE_MAKE_PROGRAM="${CMAKE_MAKE_PROGRAM}"
         ${CROSS_TOOLCHAIN_FLAGS_${target_name}} ${CMAKE_SOURCE_DIR}
         ${CROSS_TOOLCHAIN_FLAGS_${project_name}_${target_name}}
         -DLLVM_TARGET_IS_CROSSCOMPILE_HOST=TRUE
         -DLLVM_TARGETS_TO_BUILD="${targets_to_build_arg}"
         -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD="${experimental_targets_to_build_arg}"
         -DLLVM_DEFAULT_TARGET_TRIPLE="${TARGET_TRIPLE}"
         -DLLVM_TARGET_ARCH="${LLVM_TARGET_ARCH}"
         -DLLVM_ENABLE_PROJECTS="${llvm_enable_projects_arg}"
         -DLLVM_EXTERNAL_PROJECTS="${llvm_external_projects_arg}"
+        ${external_project_source_dirs}
         -DLLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN="${LLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN}"
         ${build_type_flags} ${linker_flag} ${external_clang_dir}
         ${ARGN}
     WORKING_DIRECTORY ${${project_name}_${target_name}_BUILD}
     DEPENDS CREATE_${project_name}_${target_name}
     COMMENT "Configuring ${target_name} ${project_name}...")
 
   add_custom_target(CONFIGURE_${project_name}_${target_name}