[SPARK-19999] Workaround JDK-8165231 to identify PPC64 architectures as supporting unaligned access

 java.nio.Bits.unaligned() does not return true for the ppc64le arch.
see https://bugs.openjdk.java.net/browse/JDK-8165231
## What changes were proposed in this pull request?
check architecture

## How was this patch tested?

unit test

Author: samelamin <hussam.elamin@gmail.com>
Author: samelamin <sam_elamin@discovery.com>

Closes #17472 from samelamin/SPARK-19999.