[libc] Add the 'cpp.new' as a dependency on atexit

The `atexit` function depends on the implementations in CPP/new.h but it
is not listed as a dependency. This causes the GPU build to not include
it in the `libcgpu.a` file and prevents us from using the startup code
externally. Simply add it.

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D158447

libc/src/stdlib/CMakeLists.txt

@@ -366,6 +366,7 @@ add_entrypoint_object(
     libc.src.__support.fixedvector
     libc.src.__support.blockstore
     libc.src.__support.threads.mutex
+    libc.src.__support.CPP.new
 )
 
 add_entrypoint_object(