Deprecate passing more than one value to --report

We previously decided to remove the ability for --platform (-p) to accept
multiple values due to the potential for ambiguous command lines. For
consistency, --report (-R) should not accept multiple values either.

Signed-off-by: John Pennycook <john.pennycook@intel.com>

Author: Pennycook

bin/codebasin

@@ -160,6 +160,11 @@ def main():
             "--dump will be removed in a future release.",
             DeprecationWarning,
         )
+    if len(args.reports) > 1:
+        warnings.warn(
+            "Passing more than one value to --report (-R) is deprecated.",
+            DeprecationWarning,
+        )
 
     # Determine the root directory based on the -S and -r flags.
     rootpath = None