Consider binder bitness while looking for abi references.

Binder bitness does not always correlate directly with primary arch, as
assumed earlier. For example: it is possible to have devices with
primary arch 'arm' and use 64 bit binder.

Bug: 74362434

Test: utils/create_reference_dumps.py;
      m -j vndk_package for aosp_arm64_ab, aosp_arm_ab invokes
      header-abi-diff on both arm and arm64 arches.

Test: mm -j64 in system/libhwbinder on troublesome internal target.

Merged-In: Iea0a24b57cdb3033e25b6fe126c5d5d717f45b4e
Change-Id: Iea0a24b57cdb3033e25b6fe126c5d5d717f45b4e
(cherry picked from commit 34ce67d4)