Report web compiler used with `buildEventSettings` (#125092)

Fixes https://github.com/flutter/flutter/issues/125085

packages/flutter_tools/lib/src/web/compile.dart

@@ -126,6 +126,13 @@ class WebBuilder {
     } finally {
       status.stop();
     }
+    BuildEvent(
+      'web-compile',
+      type: 'web',
+      settings: 'wasm-compile: ${compilerConfig.isWasm}',
+      flutterUsage: _flutterUsage,
+    ).send();
+
     _flutterUsage.sendTiming(
       'build',
       compilerConfig.isWasm ? 'dart2wasm' : 'dart2js',

packages/flutter_tools/test/general.shard/web/compile_web_test.dart

@@ -82,6 +82,16 @@ void main() {
     // Runs ScrubGeneratedPluginRegistrant migrator.
     expect(logger.traceText, contains('generated_plugin_registrant.dart not found. Skipping.'));
 
+    // Sends build config event
+    expect(testUsage.events, unorderedEquals(<TestUsageEvent>[
+      const TestUsageEvent(
+        'build',
+        'web',
+        label: 'web-compile',
+        parameters: CustomDimensions(buildEventSettings: 'wasm-compile: true')
+      ),
+    ]));
+
     // Sends timing event.
     final TestTimingEvent timingEvent = testUsage.timings.single;
     expect(timingEvent.category, 'build');