AAPT: Output only 64-bit arch when multiArch is true

When android:multiArch="true" in the <application> tag,
aapt dump badging should only output the 64-bit architecture
under the 'native-code' entry.

Other architectures will be emitted under the 'alt-native-code'
entry.

Bug:17061929
Change-Id: I8310b2388b06a2ed571e5e121e4989403082ba68