[compiler-rt] Don't build llvm-lit in RUNTIMES-BUILD

[jsji]

Summary

With runtimes-build, we lost map config for llvm-lit, so we can NOT run
lit from source dir anymore.
All the subdir target like: ninja check-llvm-codegen-powerpc will fail
too.

We will get some cfg error like:

File "../lvm-project/llvm/test/lit.cfg.py", line 21, in <module>
  config.test_format = lit.formats.ShTest(not llvm_config.use_lit_shell)

AttributeError: 'NoneType' object has no attribute 'use_lit_shell'

This is reset of map config in llvm-lit rebuild.
We already have llvm-lit in runtimes-build, so don't build it.

[phosek]

LGTM

[jsji]

Move up the condition to avoid unecessary warning about LLVM_EXTERNAL_LIT.

compiler-rt/CMakeLists.txt

 endif()
 pythonize_bool(COMPILER_RT_HAS_LLD)
 
 add_subdirectory(lib)
 
 if(COMPILER_RT_INCLUDE_TESTS)
   add_subdirectory(unittests)
   add_subdirectory(test)
-  if (COMPILER_RT_STANDALONE_BUILD)
+  # Don't build llvm-lit for runtimes-build, it will clean up map_config.
+  if (COMPILER_RT_STANDALONE_BUILD AND NOT RUNTIMES_BUILD)
     # If we have a valid source tree, generate llvm-lit into the bin directory.
     # The user can still choose to have the check targets *use* a different lit
     # by specifying -DLLVM_EXTERNAL_LIT, but we generate it regardless.
     if (EXISTS ${LLVM_MAIN_SRC_DIR}/utils/llvm-lit)
       # Needed for lit support in standalone builds.
       include(AddLLVM)
       add_subdirectory(${LLVM_MAIN_SRC_DIR}/utils/llvm-lit ${CMAKE_CURRENT_BINARY_DIR}/llvm-lit)
     elseif(NOT EXISTS ${LLVM_EXTERNAL_LIT})
       message(WARNING "Could not find LLVM source directory and LLVM_EXTERNAL_LIT does not"
                        "point to a valid file.  You will not be able to run tests.")
     endif()
   endif()
 endif()
 
 add_subdirectory(tools)