fix embedder on Windows - fixes #25498

pkg/analyzer/lib/source/embedder.dart

Index: pkg/analyzer/lib/source/embedder.dart
diff --git a/pkg/analyzer/lib/source/embedder.dart b/pkg/analyzer/lib/source/embedder.dart
index f77ff7c76dd12d577233a50989975e04e693cca3..97aa4c4d3eab398b6074327451b0acbc26bef174 100644
--- a/pkg/analyzer/lib/source/embedder.dart
+++ b/pkg/analyzer/lib/source/embedder.dart
@@ -156,7 +156,11 @@ class EmbedderUriResolver extends DartUriResolver {
 
   @override
   Uri restoreAbsolute(Source source) {
-    Source sdkSource = dartSdk.fromFileUri(Uri.parse(source.fullName));
+    String path = source.fullName;
+    if (path.length > 3 && path[1] == ':' && path[2] == '\\') {
+      path = '/${path[0]}:${path.substring(2).replaceAll('\\', '/')}';
+    }
+    Source sdkSource = dartSdk.fromFileUri(Uri.parse('file://$path'));
     return sdkSource?.uri;
   }
 }