Avoid double loop (#2605)

diff --git a/lib/src/entrypoint.dart b/lib/src/entrypoint.dart
index 9a29ff7..ec3d0d2 100644
--- a/lib/src/entrypoint.dart
+++ b/lib/src/entrypoint.dart
@@ -331,7 +331,7 @@
       return waitAndPrintErrors(executables.map((executable) {
         var dir = p.dirname(snapshotPathOfExecutable(executable));
         cleanDir(dir);
-        return waitAndPrintErrors(executables.map(_precompileExecutable));
+        return _precompileExecutable(executable);
       }));
     });
   }