[libc++] Don't automatically define LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS with libcxxrt

[ldionne]

Summary

libcxxrt is only used on FreeBSD and the FreeBSD CMake cache already
sets LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS to ON, as it should. This
avoids defining LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS redundantly in
a place where it doesn't belong.

[dim]

Ah I see that I added the part to HandleLibCXXABI.cmake in rG328261019f50a76b11fa625739cbf32ceb2ce2f7, while also adding an initial version of libcxx/cmake/caches/FreeBSD.cmake. If the latter is now automatically used during the build, the HandleLibCXXABI.cmake part is no longer necessary.

libcxx/cmake/Modules/HandleLibCXXABI.cmake

elseif ("${LIBCXX_CXX_ABI}" STREQUAL "system-libcxxabi")
   import_shared_library(libcxx-abi-shared c++abi)
   target_link_libraries(libcxx-abi-shared INTERFACE libcxx-abi-headers)
 
   import_static_library(libcxx-abi-static "${LIBCXX_CXX_ABI_LIBRARY_PATH}" c++abi)
   target_link_libraries(libcxx-abi-static INTERFACE libcxx-abi-headers)
 
 # Link against a system-provided libcxxrt
 elseif ("${LIBCXX_CXX_ABI}" STREQUAL "libcxxrt")
-  # libcxxrt does not provide aligned new and delete operators
-  # TODO: We're keeping this for backwards compatibility, but this doesn't belong here.
-  set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS ON)
-
   if(NOT LIBCXX_CXX_ABI_INCLUDE_PATHS)
     message(STATUS "LIBCXX_CXX_ABI_INCLUDE_PATHS not set, using /usr/include/c++/v1")
     set(LIBCXX_CXX_ABI_INCLUDE_PATHS "/usr/include/c++/v1")
   endif()
   add_library(libcxx-abi-headers INTERFACE)
   import_private_headers(libcxx-abi-headers "${LIBCXX_CXX_ABI_INCLUDE_PATHS}"
     "cxxabi.h;unwind.h;unwind-arm.h;unwind-itanium.h")
   target_compile_definitions(libcxx-abi-headers INTERFACE "-DLIBCXXRT")