[pkv/vm] Add package config to --depfile test fix

TEST=pkg/vm/test/kernel_front_end_test.dart

Change-Id: Ic359a9e1ad2caac99df8f73da9474c6757c5932f
Cq-Include-Trybots: luci.dart.try:pkg-win-release-try,pkg-win-release-arm64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/398660
Reviewed-by: Alexander Aprelev <[email protected]>
Commit-Queue: Alexander Aprelev <[email protected]>

Author: dcharkes

pkg/vm/lib/kernel_front_end.dart

@@ -535,7 +535,7 @@ Future<KernelCompilationResults> compileToKernel(
     compilerResult =
         await loadKernel(options.fileSystem, resolveInputUri(fromDillFile));
   } else {
-    ProcessedOptions processedOptions = new ProcessedOptions(
+    final processedOptions = new ProcessedOptions(
       options: options,
       inputs: [args.source!, ...args.additionalSources],
     );

pkg/vm/test/kernel_front_end_test.dart

@@ -184,7 +184,7 @@ main() {
         ]);
         expect(
           File(outputDepfile()).readAsStringSync(),
-          contains('$sdkDir/$packageConfigFile'),
+          stringContainsInOrder('$sdkDir/$packageConfigFile'.split('/')),
         );
       },
       timeout: Timeout.none,