[bgen] Add warning to the list of exceptions instead of showing it ri…

…ght away. (#21027)

This way execution won't stop if the warning was turned into an error, and
we'll get a list of all the warnings by executing once, instead of having to
re-execute after fixing each warning.

src/bgen/Generator.cs

@@ -4563,8 +4563,8 @@ void GenerateMethod (MemberInformation minfo)
 					argCount++;
 			}
 			if (minfo.Method.GetParameters ().Length != argCount) {
-				ErrorHelper.Warning (1105,
-					minfo.selector, argCount, minfo.Method, minfo.Method.GetParameters ().Length);
+				exceptions.Add (ErrorHelper.CreateWarning (1105,
+					minfo.selector, argCount, minfo.Method, minfo.Method.GetParameters ().Length));
 			}
 		}