Get et working for local web engine builds. (flutter#161825)

This PR makes a few different changes to make building the web engine
via `et` a bit smoother:
* Adds a few build steps to `local_engine.json` so that et can build
`wasm_release` and `wasm_debug_unopt` builds on Linux and Mac locally.
* Removed the part of our `generate_builder_json` step which generates
the `linux_web_engine_build.json` file. This previously used to be
generated based off of the contents of `felt_config.yaml` but now it's
just not parameterized at all, so there is no benefit to generating it
and we can just manually maintain the file now.
* Fixed an issue where the skwasm debug build was failing due to a wrong
output file being specified in the gn rule.

Author: eyebrowsoffire

engine/src/flutter/ci/builders/linux_web_engine_build.json

@@ -1,6 +1,4 @@
 {
-  "_comment": "THIS IS A GENERATED FILE. Do not edit this file directly.",
-  "_comment2": "See `generate_builder_json.dart` for the generator code",
   "builds": [
     {
       "name": "ci/wasm_release",

engine/src/flutter/ci/builders/local_engine.json

@@ -948,6 +948,108 @@
         "config": "host_release",
         "targets": []
       }
+    },
+    {
+      "name": "linux/wasm_release",
+      "drone_dimensions": [
+        "device_type=none",
+        "os=Linux"
+      ],
+      "gclient_variables": {
+        "download_android_deps": false,
+        "download_jdk": false,
+        "download_emsdk": true
+      },
+      "gn": [
+        "--web",
+        "--runtime-mode=release",
+        "--no-rbe",
+        "--no-goma"
+      ],
+      "ninja": {
+        "config": "wasm_release",
+        "targets": [
+          "flutter/web_sdk:flutter_web_sdk_archive"
+        ]
+      },
+      "cas_archive": false
+    },
+    {
+      "name": "linux/wasm_debug_unopt",
+      "drone_dimensions": [
+        "device_type=none",
+        "os=Linux"
+      ],
+      "gclient_variables": {
+        "download_android_deps": false,
+        "download_jdk": false,
+        "download_emsdk": true
+      },
+      "gn": [
+        "--web",
+        "--runtime-mode=debug",
+        "--unoptimized",
+        "--no-rbe",
+        "--no-goma"
+      ],
+      "ninja": {
+        "config": "wasm_debug_unopt",
+        "targets": [
+          "flutter/web_sdk:flutter_web_sdk_archive"
+        ]
+      },
+      "cas_archive": false
+    },
+    {
+      "name": "macos/wasm_release",
+      "drone_dimensions": [
+        "device_type=none",
+        "os=Mac"
+      ],
+      "gclient_variables": {
+        "download_android_deps": false,
+        "download_jdk": false,
+        "download_emsdk": true
+      },
+      "gn": [
+        "--web",
+        "--runtime-mode=release",
+        "--no-rbe",
+        "--no-goma"
+      ],
+      "ninja": {
+        "config": "wasm_release",
+        "targets": [
+          "flutter/web_sdk:flutter_web_sdk_archive"
+        ]
+      },
+      "cas_archive": false
+    },
+    {
+      "name": "macos/wasm_debug_unopt",
+      "drone_dimensions": [
+        "device_type=none",
+        "os=Mac"
+      ],
+      "gclient_variables": {
+        "download_android_deps": false,
+        "download_jdk": false,
+        "download_emsdk": true
+      },
+      "gn": [
+        "--web",
+        "--runtime-mode=debug",
+        "--unoptimized",
+        "--no-rbe",
+        "--no-goma"
+      ],
+      "ninja": {
+        "config": "wasm_debug_unopt",
+        "targets": [
+          "flutter/web_sdk:flutter_web_sdk_archive"
+        ]
+      },
+      "cas_archive": false
     }
   ]
 }

engine/src/flutter/lib/web_ui/dev/generate_builder_json.dart

@@ -28,10 +28,6 @@ class GenerateBuilderJsonCommand extends Command<bool> {
     final FeltConfig config = FeltConfig.fromFile(
       path.join(environment.webUiTestDir.path, 'felt_config.yaml'),
     );
-    _writeBuilderJson(
-      _generateBuilderJson([_getArtifactBuildStep()], []),
-      'linux_web_engine_build.json',
-    );
     _writeBuilderJson(
       _generateBuilderJson(
         config.testBundles.map((TestBundle bundle) => _getBundleBuildStep(bundle)).toList(),
@@ -63,33 +59,6 @@ class GenerateBuilderJsonCommand extends Command<bool> {
     return const JsonEncoder.withIndent('  ').convert(outputJson);
   }
 
-  Map<String, dynamic> _getArtifactBuildStep() {
-    return <String, dynamic>{
-      'name': 'ci/wasm_release',
-      'drone_dimensions': <String>['device_type=none', 'os=Linux', 'cores=32'],
-      'gclient_variables': <String, dynamic>{
-        'download_android_deps': false,
-        'download_jdk': false,
-        'download_emsdk': true,
-      },
-      'gn': <String>['--web', '--runtime-mode=release', '--no-rbe', '--no-goma'],
-      'ninja': <String, dynamic>{
-        'config': 'wasm_release',
-        'targets': <String>['flutter/web_sdk:flutter_web_sdk_archive'],
-      },
-      'archives': <dynamic>[
-        <String, dynamic>{
-          'name': 'wasm_release',
-          'base_path': 'out/wasm_release/zip_archives/',
-          'type': 'gcs',
-          'include_paths': <String>['out/wasm_release/zip_archives/flutter-web-sdk.zip'],
-          'realm': 'production',
-        },
-      ],
-      'cas_archive': false,
-    };
-  }
-
   Map<String, dynamic> _getBundleBuildStep(TestBundle bundle) {
     return <String, dynamic>{
       'name': 'web_tests/test_bundles/${bundle.name}',

engine/src/flutter/third_party/canvaskit/BUILD.gn

@@ -143,7 +143,7 @@ copy("skwasm_st_group") {
   ]
   if (is_debug) {
     if (!wasm_use_dwarf) {
-      sources += [ "$root_out_dir/skwasm_st/skwasm.wasm.map" ]
+      sources += [ "$root_out_dir/skwasm_st/skwasm_st.wasm.map" ]
     }
   }
   outputs = [ "$root_out_dir/flutter_web_sdk/canvaskit/{{source_file_part}}" ]