RFR: Fix Shenandoah non-PCH build

[Zhengyu Gu]

Non-PCH build broke again.

http://cr.openjdk.java.net/~zgu/shenandoah/sh-non-pch/webrev.00/index.html

Test:
   non-PCH builds (fastdebug and release)


Thanks,

-Zhengyu