Add missing sources to libclang_rt Makefiles, clean up unneeded ones

During the llvm-17 merge, a few new source files were not added to the
libclang_rt Makefiles, in particular sanitizer_thread_arg_retval.cpp
which is now required for AddressSanitizer and MemorySanitizer. Also,
MemorySanitizer now requires msan_dl.cpp.

While here, clean out a number of source files that compile into nothing
(because they only contain non-FreeBSD parts). Also, remove a duplicated
instance of tsan_new_delete.cpp from libclang_rt.tsan, since it is only
supposed to live in libclang_rt.tsan_cxx.

PR: 275854
Reported by: jbeich
MFC after: 1 month