[libc] Correctly pass 'CXX_STANDARD' to the packaged GPU build

[jhuber6]

Summary

We need to perform the GPU build separately. The CXX_STANDARD option
was not being passed properly.

libc/cmake/modules/LLVMLibCObjectRules.cmake

cmake_parse_arguments(
     "" # No optional arguments
     "NAME;CXX_STANDARD" # Single value arguments
     "SRCS;HDRS;DEPENDS;COMPILE_OPTIONS;FLAGS"  # Multi value arguments
     ${ARGN}
   )
 
   set(include_dirs ${LIBC_BUILD_DIR}/include ${LIBC_SOURCE_DIR} ${LIBC_BUILD_DIR})
   set(common_compile_options ${ADD_GPU_OBJ_COMPILE_OPTIONS})
+  if(NOT ADD_GPU_OBJ_CXX_STANDARD)
+    set(ADD_GPU_OBJ_CXX_STANDARD ${CMAKE_CXX_STANDARD})
+  endif()
 
   foreach(add_gpu_obj_src ${ADD_GPU_OBJ_SRCS})
     # The packaged version will be built for every target GPU architecture. We do
     # this so we can support multiple accelerators on the same machine.
     foreach(gpu_arch ${LIBC_GPU_ARCHITECTURES})
       get_filename_component(src_name ${add_gpu_obj_src} NAME)
       set(gpu_target_name ${fq_target_name}.${src_name}.${gpu_arch})
       set(compile_options ${ADD_GPU_OBJ_COMPILE_OPTIONS})
foreach(gpu_arch ${LIBC_GPU_ARCHITECTURES})
         OBJECT
         ${add_gpu_obj_src}
         ${ADD_GPU_OBJ_HDRS}
       )
 
       target_compile_options(${gpu_target_name} PRIVATE ${compile_options})
       target_include_directories(${gpu_target_name} PRIVATE ${include_dirs})
       target_compile_definitions(${gpu_target_name} PRIVATE LIBC_COPT_PUBLIC_PACKAGING)
+      set_target_properties(
+        ${gpu_target_name}
+        PROPERTIES
+          CXX_STANDARD ${ADD_GPU_OBJ_CXX_STANDARD}
+      )
       if(ADD_GPU_OBJ_DEPENDS)
         add_dependencies(${gpu_target_name} ${ADD_GPU_OBJ_DEPENDS})
       endif()
 
       # Append this target to a list of images to package into a single binary.
       set(input_file $<TARGET_OBJECTS:${gpu_target_name}>)
       list(APPEND packager_images
            --image=file=${input_file},arch=${gpu_arch},triple=${gpu_target_triple})
function(create_object_library fq_target_name)
   # export several different targets at once, e.g. for both Nvidia and AMD.
   if(LIBC_TARGET_ARCHITECTURE_IS_GPU AND NOT ${ADD_OBJECT_NO_GPU_BUNDLE})
     _build_gpu_objects(
       ${fq_target_name}
       ${internal_target_name}
       SRCS ${ADD_OBJECT_SRCS}
       HDRS ${ADD_OBJECT_HDRS}
       DEPENDS ${fq_deps_list}
+      CXX_STANDARD ${ADD_OBJECT_CXX_STANDARD}
       COMPILE_OPTIONS ${compile_options}
     )
   else()
     add_library(
       ${fq_target_name}
       EXCLUDE_FROM_ALL
       OBJECT
       ${ADD_OBJECT_SRCS}
function(create_entrypoint_object fq_target_name)
   # export several different targets at once, e.g. for both Nvidia and AMD.
   if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
     _build_gpu_objects(
       ${fq_target_name}
       ${internal_target_name}
       SRCS ${ADD_ENTRYPOINT_OBJ_SRCS}
       HDRS ${ADD_ENTRYPOINT_OBJ_HDRS}
       COMPILE_OPTIONS ${common_compile_options}
+      CXX_STANDARD ${ADD_ENTRYPOINT_OBJ_CXX_STANDARD}
       DEPENDS ${full_deps_list}
       FLAGS "${ADD_ENTRYPOINT_OBJ_FLAGS}"
     )
   else()
     add_library(
       ${internal_target_name}
       # TODO: We don't need an object library for internal consumption.
       # A future change should switch this to a normal static library.