RFR(XS): 8245070: 32-bit builds are broken after JDK-8242524

[Yumin Qi]

Hi,

  Please review the xsmall change for
  bug: 8245070: https://bugs.openjdk.java.net/browse/JDK-8245070
  webrev: http://cr.openjdk.java.net/~minqi/2020/8245070/webrev-00/
  The change of 8245070 broke build for 32 bits, since no compressed 
oops on 32 bits. Guard the change for 64 bits only.
  I could not build 32 bits --- have no 32 bit platform to make sure of 
the change, so please give a detail look. The variable 
OPENJDK_TARGET_CPU_BITS is copied from other file.

Thanks
Yumin