nx_smoke_nxc_pipeline.nx

Replay nxc.nx's pipeline on the baked-in demo, reporting at each stage so we can see exactly where stage 4 is failing. Returns: 1 = lex_source returned NULL 2 = parse_module returned NULL 3-9 = opt/regalloc/riscv stage threw something we'd need to instrument differently (just runs) 100 = OK, asm_pos was 0 (nothing emitted) 101 = OK, asm_pos > 0, code_len == 0 102 = OK, asm_pos > 0, code_len < 0 -- distinguished below 200 = code_len == -1 (unknown mnemonic) 201 = code_len == -2 (pass 1 fail) 202 = code_len == -3 (pass 2 fail) N = code_len when 0 < N < 100 (success)