[lldb][cmake] Move remove_module_flags macro to AddLLDB.cmake

Summary: This is currently hidden in the Host CMakeLists but we should also use this macro in other parts of LLDB where we have ObjC++ sources (see D74891)

Reviewers: JDevlieghere

Reviewed By: JDevlieghere

Subscribers: mgorny, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D75164