[BOLT][Wrapper] Don't compare output upon error exit code

[Amir]

Summary

Fix llvm-bolt-wrapper to skip output file checks if llvm-bolt exits with error
code.

Test Plan:

• checkout to revision with invalid NFC mismatch in is-strip.s test (e.g. 056af487831fb573e6895901d1e48f93922f9635~)
• run nfc-check-setup.py
• run bin/llvm-lit -a tools/bolt/test/X86/is-strip.s

bolt/utils/llvm-bolt-wrapper.py

else:
         main_out = wait(main_bolt, main_f)
     cmp_out = wait(cmp_bolt, cmp_f)
 
     # check exit code
     if main_bolt.returncode != cmp_bolt.returncode:
         print(tmp)
         exit("exitcode mismatch")
 
+    # don't compare output upon unsuccessful exit
+    if main_bolt.returncode != 0:
+        cfg.SKIP_BINARY_CMP = True
+
     # compare logs, skip_end=1 skips the line with time
     out = compare_logs(main_out, cmp_out, skip_end=1, str_input=False) if cfg.COMPARE_OUTPUT else None
     if out:
         print(tmp)
         print(fmt_cmp(out))
         write_to(fmt_cmp(out), os.path.join(tmp, 'summary.txt'))
         exit("logs mismatch")
 
     if os.path.basename(sys.argv[0]) == 'llvm-boltdiff': # boltdiff mode
         # no output binary to compare, so just exit
         clean_exit(tmp, main_out, main_bolt.returncode, cfg)
 
     # compare binaries (using cmp)
     main_binary = args[args.index('-o')+1]
     cmp_binary = cmp_args[cmp_args.index('-o')+1]
     if main_binary == '/dev/null':
         assert cmp_binary == '/dev/null'
         cfg.SKIP_BINARY_CMP = True
 
     # report binary timing as csv: output binary; base bolt real; cmp bolt real
     report_real_time(main_binary, main_out, cmp_out, cfg)
 
+    if not cfg.SKIP_BINARY_CMP:
         # check if files exist
         main_exists = os.path.exists(main_binary)
         cmp_exists = os.path.exists(cmp_binary)
         if main_exists and cmp_exists:
             # proceed to comparison
             pass
         elif not main_exists and not cmp_exists:
             # both don't exist, assume it's intended, skip comparison
             clean_exit(tmp, main_out, main_bolt.returncode, cfg)
         elif main_exists:
             assert not cmp_exists
             exit(f"{cmp_binary} doesn't exist")
         else:
             assert not main_exists
             exit(f"{main_binary} doesn't exist")
 
-    if not cfg.SKIP_BINARY_CMP:
         cmp_proc = subprocess.run(['cmp', '-b', main_binary, cmp_binary],
                                   capture_output=True, text=True)
         if cmp_proc.returncode:
             # check if output is an ELF file (magic bytes)
             with open(main_binary, 'rb') as f:
                 magic = f.read(4)
                 if magic != b'\x7fELF':
                     exit("output mismatch")