llvm/llvm/test/tools/UpdateTestChecks/update_test_checks/pre-process.test

## Test that update_test_checks.py can run pre-processing commands.
# RUN: cp -f %S/Inputs/pre-process.ll %t.ll && %update_test_checks --function-signature %t.ll
# RUN: diff -u %t.ll %S/Inputs/pre-process.ll.expected
## Check that running the script again does not change the result:
# RUN: %update_test_checks %t.ll
# RUN: diff -u %t.ll %S/Inputs/pre-process.ll.expected