driver: implement post-target run argv semantics

selfhost/cmd/ww/main.ww

@@ -9832,12 +9832,11 @@ fn dorun(selfdir: *u8, argv: **u8, argc: i32, start: i32) i32 = {
 			}; }; }; };
 			i += 1;
 		} else {
-			if (src == nil) {
-				src = p;
-				i += 1;
-			} else {
-				passstart = i;
-			};
+			src = p;
+			i += 1;
+			// The first target ends driver option parsing.  The exact
+			// suffix, including flag-like operands, belongs to the program.
+			passstart = i;
 		};
 		};
 	};