Use kPointerSize when cross-compiling. am: b6c230117d am: 2f7444b38d

Original change: https://android-review.googlesource.com/c/platform/art/+/2402709

Change-Id: Ib9767a1d40d945250e1aa75d4b161087cac393a2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>