Autogen: Add clang --target= flag to compiler predefines command
Respect the compiler target value CMAKE_<LANG>_COMPILER_TARGET in CMAKE_<LANG>_COMPILER_PREDEFINES_COMMAND to get proper moc predefines during cross-compiling.
For Android, when we set CMAKE_<LANG>_COMPILER_TARGET to the Android target architecture, add it to CMAKE_<LANG>_COMPILER_PREDEFINES_COMMAND also. This is needed to make moc predefines aware of __ANDROID__.
Fixes: #18425 (closed)