fix: empty exclude value in option file badly handled (#4546)

lib/tooling/base-tool.ts

@@ -73,6 +73,12 @@ export class BaseTool implements ITool {
             }
             // Even if the include key is truthy, we fall back to the exclusion list.
         }
+
+        // an empty value (e.g. 'tool.foo.exclude=') yields a single empty
+        // string in the array, not an empty array.
+        if (this.tool.exclude.length === 1 && this.tool.exclude[0] === '')
+            return false;
+
         return this.tool.exclude.find(excl => compilerId.includes(excl)) !== undefined;
     }