Comment by retrac

LLVM includes an equivalent to binutils, with a macro assembler, linker, objdump with disassembler, library tools, handling formats like ELF and raw binary etc.

LLVM-MOS includes all of that. It is the same process as using LLVM to cross-assemble targeting an embedded ARM board. Same GNU assembler syntax just with 6502 opcodes. This incidentally makes LLVM-MOS one of the best available 6502 assembly development environments, if you like Unix-style cross-assemblers.