log to file for build.dart, check for SUCCESS token

thermion_dart/hook/build.dart

@@ -6,9 +6,19 @@ import 'package:native_toolchain_c/native_toolchain_c.dart';
 
 void main(List<String> args) async {
   await build(args, (config, output) async {
+    var logDir = Directory(
+        "${config.packageRoot.toFilePath()}/.dart_tool/thermion_dart/log/");
+    if (!logDir.existsSync()) {
+      logDir.createSync();
+    }
+    var logFile = File(logDir.path + "/build.log");
 
-    final logger = Logger("")..level = Level.ALL
-        ..onRecord.listen((record) => print(record.message));
+    final logger = Logger("")
+      ..level = Level.ALL
+      ..onRecord.listen((record) => logFile.writeAsStringSync(
+          record.message + "\n",
+          mode: FileMode.append,
+          flush: true));
 
     var platform = config.targetOS.toString().toLowerCase();
 
@@ -71,7 +81,7 @@ void main(List<String> args) async {
     } else {
       libs.add("stdc++");
     }
-    final flags = [];
+    final flags = [];  //"-fsanitize=address"];
     final defines = <String, String?>{};
     var frameworks = [];
 
@@ -85,7 +95,15 @@ void main(List<String> args) async {
     }
 
     if (platform == "ios") {
-      frameworks.addAll(['Foundation', 'CoreGraphics', 'QuartzCore', 'GLKit', "Metal", 'CoreVideo', 'OpenGLES']);
+      frameworks.addAll([
+        'Foundation',
+        'CoreGraphics',
+        'QuartzCore',
+        'GLKit',
+        "Metal",
+        'CoreVideo',
+        'OpenGLES'
+      ]);
     } else if (platform == "macos") {
       frameworks.addAll([
         'Foundation',
@@ -162,7 +180,7 @@ void main(List<String> args) async {
   });
 }
 
-String _FILAMENT_VERSION ="v1.51.2";
+String _FILAMENT_VERSION = "v1.51.2";
 String _getLibraryUrl(String platform, String mode) {
   return "https://pub-c8b6266320924116aaddce03b5313c0a.r2.dev/filament-${_FILAMENT_VERSION}-${platform}-${mode}.zip";
 }
@@ -171,7 +189,6 @@ String _getLibraryUrl(String platform, String mode) {
 // Download precompiled Filament libraries for the target platform from Cloudflare.
 //
 Future<Directory> getLibDir(BuildConfig config, Logger logger) async {
-
   var platform = config.targetOS.toString().toLowerCase();
 
   // Except on Windows, most users will only need release builds of Filament.
@@ -183,11 +200,12 @@ Future<Directory> getLibDir(BuildConfig config, Logger logger) async {
   // However, if you know what you're doing, you can change "release" to "debug" below.
   // TODO - check if we can pass this as a CLI compiler flag
   var mode = "release";
-    if(platform == "windows") {
+  if (platform == "windows") {
     mode = config.buildMode == BuildMode.debug ? "debug" : "release";
   }
 
-    var libDir = Directory("${config.packageRoot.toFilePath()}/.dart_tool/thermion_dart/lib/${_FILAMENT_VERSION}/$platform/$mode/");
+  var libDir = Directory(
+      "${config.packageRoot.toFilePath()}/.dart_tool/thermion_dart/lib/${_FILAMENT_VERSION}/$platform/$mode/");
 
   if (platform == "android") {
     final archExtension = switch (config.targetArchitecture) {
@@ -198,9 +216,10 @@ Future<Directory> getLibDir(BuildConfig config, Logger logger) async {
       _ => throw FormatException('Invalid')
     };
     libDir = Directory("${libDir.path}/$archExtension/");
-    } else if(platform == "windows") {
-      if(config.targetArchitecture != Architecture.x64) {
-        throw Exception("Unsupported architecture : ${config.targetArchitecture}");
+  } else if (platform == "windows") {
+    if (config.targetArchitecture != Architecture.x64) {
+      throw Exception(
+          "Unsupported architecture : ${config.targetArchitecture}");
     }
   }
 
@@ -208,22 +227,23 @@ Future<Directory> getLibDir(BuildConfig config, Logger logger) async {
 
   final filename = url.split("/").last;
 
-    // Assume that the libraries exist if the directory containing them exists.
-    if (!libDir.existsSync()) {
-
+  // We will write an empty file called success to the unzip directory after successfully downloading/extracting the prebuilt libraries.
+  // If this file already exists, we assume everything has been successfully extracted and skip
   final unzipDir = platform == "android" ? libDir.parent.path : libDir.path;
-
+  final successToken = File("$unzipDir/success");
   final libraryZip = File("$unzipDir/$filename");
 
-      if(libraryZip.existsSync()) {
+  if (!successToken.existsSync()) {
+    if (libraryZip.existsSync()) {
       libraryZip.deleteSync();
     }
 
-      if(!libraryZip.parent.existsSync()) {
+    if (!libraryZip.parent.existsSync()) {
       libraryZip.parent.createSync(recursive: true);
     }
 
-      logger.info("Downloading prebuilt libraries for $platform/$mode from $url to ${libraryZip}, files will be unzipped to ${unzipDir}");
+    logger.info(
+        "Downloading prebuilt libraries for $platform/$mode from $url to ${libraryZip}, files will be unzipped to ${unzipDir}");
     final request = await HttpClient().getUrl(Uri.parse(url));
     final response = await request.close();
 
@@ -243,6 +263,7 @@ Future<Directory> getLibDir(BuildConfig config, Logger logger) async {
         await d.create(recursive: true);
       }
     }
+    successToken.writeAsStringSync("SUCCESS");
   }
   return libDir;
 }