[test_runner] Fix a few tests after making test runner default to host architecture

This is a follow up to: https://dart-review.googlesource.com/c/sdk/+/426463

Change-Id: I4eac63328b5fa2a2576e6f49424e3bff12f2899d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/426840
Reviewed-by: Alexander Thomas <[email protected]>

Author: mkustermann

pkg/smith/test/configuration_test.dart

@@ -165,9 +165,9 @@ void main() {
                 System.linux)));
       });
 
-      test("architecture defaults to 'x64'", () {
+      test("architecture defaults to host architecture", () {
         expect(Configuration.parse("dart2js-debug-vm-linux", {}).architecture,
-            equals(Architecture.x64));
+            equals(Architecture.host));
       });
 
       test("compiler defaults to runtime's default compiler", () {
@@ -213,7 +213,7 @@ void main() {
               "hot-reload-rollback": true,
               "use-sdk": true
             }),
-            equals(Configuration("dart2js", Architecture.x64, Compiler.dart2js,
+            equals(Configuration("dart2js", Architecture.host, Compiler.dart2js,
                 Mode.release, Runtime.d8, System.host,
                 nnbdMode: NnbdMode.weak,
                 builderTag: "the tag",

pkg/smith/test/test_matrix_test.dart

@@ -38,7 +38,7 @@ void main() {
               enableAsserts: true)));
       expect(
           testMatrix.configurations[2],
-          equals(Configuration("ddc-hostasserts-linux-d8", Architecture.x64,
+          equals(Configuration("ddc-hostasserts-linux-d8", Architecture.host,
               Compiler.ddc, Mode.release, Runtime.d8, System.linux,
               enableHostAsserts: true)));
     });