[libc++] Explicitly request new/delete in libc++ for Win to ARM Linux builds

[ldionne]

Summary

Since 9b40ee8eb0c1, new/delete must be requested explicitly during the
CMake configuration if one wants these definitions to appear in libc++.

[ldionne]

This should fix the Win to ARM Linux bot failures seen by @rsmith in https://reviews.llvm.org/D68269.

[broadwaylamb]

LGTM

clang/cmake/caches/CrossWinToARMLinux.cmake

 
 set(LIBCXX_USE_COMPILER_RT                  ON CACHE BOOL "")
 set(LIBCXX_TARGET_TRIPLE                    "${CMAKE_C_COMPILER_TARGET}" CACHE STRING "")
 set(LIBCXX_SYSROOT                          "${DEFAULT_SYSROOT}" CACHE STRING "")
 set(LIBCXX_ENABLE_SHARED                    OFF CACHE BOOL "")
 set(LIBCXX_CXX_ABI                          "libcxxabi" CACHE STRING "")
 set(LIBCXX_CXX_ABI_INCLUDE_PATHS            "${LLVM_PROJECT_DIR}/libcxxabi/include" CACHE PATH "")
 set(LIBCXX_CXX_ABI_LIBRARY_PATH             "${CMAKE_BINARY_DIR}/lib/${LIBCXX_TARGET_TRIPLE}/c++" CACHE PATH "")
+set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS    ON CACHE BOOL "")
 
 set(BUILTINS_CMAKE_ARGS                     "-DCMAKE_SYSTEM_NAME=Linux;-DCMAKE_AR=${CMAKE_AR}" CACHE STRING "")
 set(RUNTIMES_CMAKE_ARGS                     "-DCMAKE_SYSTEM_NAME=Linux;-DCMAKE_AR=${CMAKE_AR}" CACHE STRING "")
 
 find_package(Python3 COMPONENTS Interpreter)
 
 # Remote test configuration.
 if(DEFINED REMOTE_TEST_HOST)