Explcitly check for argument name in the test.

Author: quic-akaryaki

llvm/test/tools/llvm-objcopy/tool-options.test

@@ -1,4 +1,6 @@
 ## An error must be reported if a required argument value is missing.
-# RUN: not llvm-objcopy --only-section 2>&1 | FileCheck --check-prefix=CHECK-NO-VALUE %s
-# RUN: not llvm-objcopy -O 2>&1 | FileCheck --check-prefix=CHECK-NO-VALUE %s
-# CHECK-NO-VALUE: error: argument to '{{.*}}' is missing
+# RUN: not llvm-objcopy --only-section 2>&1 | FileCheck --check-prefix=CHECK-NO-VALUE-ONLY-SECTION %s
+# CHECK-NO-VALUE-ONLY-SECTION: error: argument to '--only-section' is missing
+
+# RUN: not llvm-objcopy -O 2>&1 | FileCheck --check-prefix=CHECK-NO-VALUE-O %s
+# CHECK-NO-VALUE-O: error: argument to '-O' is missing