Merge commit '728030a45280' from llvm.org/release/21.x into stable/21.x

Author: git apple-llvm automerger

compiler-rt/test/lit.common.cfg.py

@@ -506,7 +506,7 @@ def get_ios_commands_dir():
 # Define %arch to check for architecture-dependent output.
 config.substitutions.append(("%arch", (config.host_arch)))
 
-if config.host_os == "Windows":
+if os.name == "nt":
     # FIXME: This isn't quite right. Specifically, it will succeed if the program
     # does not crash but exits with a non-zero exit code. We ought to merge
     # KillTheDoctor and not --crash to make the latter more useful and remove the