Build: Fix DEX2OAT_TARGET_CPU_VARIANT setting

The secondary variant fallback was not set. The build system expects
the variants, so system properties were malformed for x86-64:

  [dalvik.vm.isa.x86.variant]: [dalvik.vm.isa.x86.features=default]

Bug: 24989387
Change-Id: Idbf54f81494f2650ad56080305807fd6b7ed4161
1 file changed