RFR (XS) 8232882: GCC 4.8.5 build failure after JDK-8211073

[Aleksey Shipilev]

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8232882

See the bug. There is an awkwardness in MemNode::calculate_adr_type that is exposed by recent build
config change that produces warning in release config. The simplest way out I see is to avoid the
dead store under PRODUCT. I believe cross_check is only ever used under ASSERT in that method.

Fix:
  https://cr.openjdk.java.net/~shade/8232882/webrev.01/

Testing: gcc 4.8.5, 7.4.0 builds, both fastdebug and release; jdk-submit (running)

-- 
Thanks,
-Aleksey