[dart2wasm] Fix wasm unit test structure.

Previously these were being run with the standard "pkg" unit test suite.
All the other backends have their own unit test suite so this introduces
one for dart2wasm.

This ensures the tests run with the correct fileset (including d8).

Change-Id: I29cd0048a4d6731da3a20110f6e496fe7da0c3b6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/454760
Commit-Queue: Nate Biggs <[email protected]>
Reviewed-by: Martin Kustermann <[email protected]>

Author: natebiggs

tools/bots/test_matrix.json

@@ -215,6 +215,17 @@
         "use-sdk": true
       }
     },
+    "wasm-unittest-asserts-(linux|mac)": {
+      "options": {
+        "builder-tag": "wasm",
+        "compiler": "dartk",
+        "enable-asserts": true,
+        "mode": "release",
+        "runtime": "vm",
+        "timeout": 240,
+        "use-sdk": true
+      }
+    },
     "web-dev-unittest-asserts-(linux|win)": {
       "options": {
         "builder-tag": "ddc",
@@ -2663,11 +2674,20 @@
         },
         {
           "name": "dart2wasm unit tests",
+          "arguments": [
+            "-nwasm-unittest-asserts-linux",
+            "pkg/dart2wasm"
+          ],
+          "shards": 1,
+          "fileset": "dart2wasm_hostasserts"
+        },
+        {
+          "name": "dart2wasm dry run tests",
           "script": "out/ReleaseX64/dart-sdk/bin/dart",
           "testRunner": true,
           "arguments": [
             "pkg/dart2wasm/test/dry_run/dry_run_test.dart",
-            "-ndart2wasm-asserts-linux-chrome"
+            "-nwasm-unittest-asserts-linux"
           ]
         }
       ]
@@ -3111,7 +3131,7 @@
           "name": "package unit tests",
           "arguments": [
             "-nunittest-asserts-${mode}-${system}-${arch}",
-            "pkg/pkg/(?!(analyzer*|analysis_server|analysis_server_plugin|compiler|dev_compiler|js_runtime|front_end|kernel|frontend_server|nnbd_migration|dartdev/test/native_assets|vm_service)/)"
+            "pkg/pkg/(?!(analyzer*|analysis_server|analysis_server_plugin|compiler|dart2wasm|dev_compiler|js_runtime|front_end|kernel|frontend_server|nnbd_migration|dartdev/test/native_assets|vm_service)/)"
           ],
           "shards": 3,
           "fileset": "vm"
@@ -3227,7 +3247,7 @@
           "name": "package unit tests",
           "arguments": [
             "-nunittest-asserts-${mode}-${system}-${arch}",
-            "pkg/pkg/(?!(analyzer*|analysis_server|analysis_server_plugin|compiler|dev_compiler|js_runtime|front_end|kernel|frontend_server|nnbd_migration|dartdev/test/native_assets|vm_service)/)"
+            "pkg/pkg/(?!(analyzer*|analysis_server|analysis_server_plugin|compiler|dart2wasm|dev_compiler|js_runtime|front_end|kernel|frontend_server|nnbd_migration|dartdev/test/native_assets|vm_service)/)"
           ]
         }
       ]