Dart format with latest SDK (dart-lang/package_config#111)

pkgs/package_config/lib/src/util_io.dart

diff --git a/pkgs/package_config/lib/src/util_io.dart b/pkgs/package_config/lib/src/util_io.dart
index 8e5f0b8..9c48f04 100644
--- a/pkgs/package_config/lib/src/util_io.dart
+++ b/pkgs/package_config/lib/src/util_io.dart
@@ -98,7 +98,9 @@
   var buffer = StringBuffer();
   var separator = "";
   for (var part in parts) {
-    buffer..write(separator)..write(part);
+    buffer
+      ..write(separator)
+      ..write(part);
     separator =
         part.endsWith(Platform.pathSeparator) ? "" : Platform.pathSeparator;
   }