Fix benchmarksByTag with a custom test list. Array.prototype.concat

returns a new array and doesn't modify the `this` one.

Author: kmiller68

JetStreamDriver.js

@@ -2430,7 +2430,7 @@ function processTestList(testList)
     for (let name of benchmarkNames) {
         name = name.toLowerCase();
         if (benchmarksByTag.has(name))
-            benchmarks.concat(findBenchmarksByTag(name));
+            benchmarks = benchmarks.concat(findBenchmarksByTag(name));
         else
             benchmarks.push(findBenchmarkByName(name));
     }