[CMake] Load LLVMConfig for standalone build of builtins

[Hahnfeld]

Summary

Therefore move some code into reusable macros.

[beanz]

This isn't the right solution here. We should instead make the builtins build load LLVMConfig.cmake (if available) and construct the value from the TARGET_TRIPLE the same way the sanitizer build does. If LLVMConfig.cmake isn't available we should make the builtin build error out during configuration that it needs the TARGET_TRIPLE specified.

-Chris

[Hahnfeld]

Make changes in compiler-rt to load LLVMConfig

[Hahnfeld]

In D22866#500834, @beanz wrote:

This isn't the right solution here. We should instead make the builtins build load LLVMConfig.cmake (if available) and construct the value from the TARGET_TRIPLE the same way the sanitizer build does. If LLVMConfig.cmake isn't available we should make the builtin build error out during configuration that it needs the TARGET_TRIPLE specified.

-Chris

Hi Chris,

I'm absolutely no CMake expert, but the changes seem to work for me.

Thanks,
Jonas

[beanz]

LGTM.

runtimes/CMakeLists.txt

 
 else() # if this is included from LLVM's CMake
   include(LLVMExternalProjectUtils)
 
   # If compiler-rt is present we need to build the builtin libraries first. This
   # is required because the other runtimes need the builtin libraries present
   # before the just-built compiler can pass the configuration tests.
   if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/compiler-rt)
+    string(REPLACE "-" ";" TARGET_TRIPLE_LIST ${TARGET_TRIPLE})
+    list(GET TARGET_TRIPLE_LIST 0 COMPILER_RT_DEFAULT_TARGET_ARCH)
     llvm_ExternalProject_Add(builtins
                              ${CMAKE_CURRENT_SOURCE_DIR}/compiler-rt/lib/builtins
                              PASSTHROUGH_PREFIXES COMPILER_RT
                              USE_TOOLCHAIN)
     set(deps builtins)
   endif()
 
   # We create a list the names of all the runtime projects in all uppercase and