Automerge: [cmake] LLVM_BUILTINS_TARGET='default' should bootstrap builtins without compiler-rt (#171536)

Author: ndrewh

llvm/runtimes/CMakeLists.txt

@@ -34,6 +34,13 @@ function(get_compiler_rt_path path)
       return()
     endif()
   endforeach()
+
+  # If LLVM_BUILTIN_TARGETS is specified, we still need
+  # to locate the compiler-rt runtime to be able to build builtins.
+  # This supports bootstrapping builtins without compiler-rt.
+  if (LLVM_BUILTIN_TARGETS)
+    set(${path} "${CMAKE_CURRENT_SOURCE_DIR}/../../compiler-rt" PARENT_SCOPE)
+  endif()
 endfunction()
 
 include(LLVMExternalProjectUtils)