Issue 30006. Don't flush on write to FileByteStore.

pkg/front_end/lib/src/incremental/file_byte_store.dart

Index: pkg/front_end/lib/src/incremental/file_byte_store.dart
diff --git a/pkg/front_end/lib/src/incremental/file_byte_store.dart b/pkg/front_end/lib/src/incremental/file_byte_store.dart
index 083b6768c01b875ae70dbb0ec24d90900e01b851..7e7cc3763ba4bb642e23e25fe0d975ec03eefabb 100644
--- a/pkg/front_end/lib/src/incremental/file_byte_store.dart
+++ b/pkg/front_end/lib/src/incremental/file_byte_store.dart
@@ -159,7 +159,7 @@ class FileByteStore implements ByteStore {
   void put(String key, List<int> bytes) {
     try {
       File tempFile = _getFileForKey(_tempName);
-      tempFile.writeAsBytesSync(bytes, flush: true);
+      tempFile.writeAsBytesSync(bytes);
       File file = _getFileForKey(key);
       tempFile.renameSync(file.path);
     } catch (_) {}