[VM] Fix accidental double assignment
[VM] Fix accidental double assignment

This broke ARM on a non-standard compiler.

Change-Id: Idf4e7d5ea9072e6e07d796dc676ec3e7afd6f235
Reviewed-on: https://dart-review.googlesource.com/44786
Reviewed-by: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>
Commit-Queue: Martin Kustermann <a35dd5b79fac84b2bb3b026a16b8becc55af5961@google.com>

dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk