Setup testing target dependencies for default runtimes

[beanz]

Summary

The default runtimes targets aren't getting their dependencies configured correctly which results in check-runtimes failing when built from a clean build.

[phosek]

LGTM

llvm/runtimes/CMakeLists.txt

configure_file(
       @ONLY
     )
   endif()
 
   function(runtime_default_target)
     cmake_parse_arguments(ARG "" "" "DEPENDS;PREFIXES" ${ARGN})
 
     include(${LLVM_BINARY_DIR}/runtimes/Components.cmake OPTIONAL)
+    set(SUB_CHECK_TARGETS ${SUB_CHECK_TARGETS} PARENT_SCOPE)
     set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${LLVM_BINARY_DIR}/runtimes/Components.cmake)
 
     foreach(runtime_name ${runtime_names})
       list(APPEND extra_targets
         ${runtime_name}
         install-${runtime_name}
         install-${runtime_name}-stripped)
       if(LLVM_INCLUDE_TESTS)
else() # if this is included from LLVM's CMake
   if(runtimes)
     # Create a runtimes target that uses this file as its top-level CMake file.
     # The runtimes target is a configuration of all the runtime libraries
     # together in a single CMake invocaiton.
     if(NOT LLVM_RUNTIME_TARGETS)
       runtime_default_target(
         DEPENDS ${deps}
         PREFIXES ${prefixes})
+      set(test_targets check-runtimes)
     else()
       if("default" IN_LIST LLVM_RUNTIME_TARGETS)
         runtime_default_target(
           DEPENDS ${deps}
           PREFIXES ${prefixes})
         list(REMOVE_ITEM LLVM_RUNTIME_TARGETS "default")
       else()
         add_custom_target(runtimes)