Add the number of missing arguments in the test for checking.

Author: quic-akaryaki

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

@@ -1,6 +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-ONLY-SECTION %s
-# CHECK-NO-VALUE-ONLY-SECTION: error: argument to '--only-section' is missing
+# CHECK-NO-VALUE-ONLY-SECTION: error: argument to '--only-section' is missing (expected 1 value(s))
 
 # 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
+# CHECK-NO-VALUE-O: error: argument to '-O' is missing (expected 1 value(s))