Fix binaries and symlinks for prefer32

Track the primary architecture selected for each class based on the
module's multilib setting and the global config.  Fixes building
binaries with multlib set to first and DevicePrefer32BitExecutables set,
and fixes symlinks to binaries with multilib set to prefer32.

Bug: 31452121
Test: mmma -j art HOST_PREFER_32_BIT=true
Change-Id: I75094df42f3273f6d613e4058eaa565957174c28