Delete stale compiled files.

sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart

Index: sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart b/sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart
index 99f15f55c7560a3c4e45ae6f0e9d369b9d87a5e0..aed7cd1bcff73f94387d5a698b941a5569549937 100644
--- a/sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart
+++ b/sdk/lib/_internal/pub_generated/lib/src/barback/asset_environment.dart
@@ -132,7 +132,6 @@ class AssetEnvironment {
           if (result.success) {
             log.message("Precompiled ${_formatExecutable(id)}.");
           } else {
-            deleteEntry(snapshotPath);
             throw new ApplicationException(
                 log.yellow("Failed to precompile " "${_formatExecutable(id)}:\n") +
                     result.stderr.join('\n'));