Fix 64-bit build break.

Master (aosp and internal) has been broken for nearly two days now.

Was broken by https://android-review.googlesource.com/#/c/212244/
because no one checked 64-bit before merging.

No one noticed post-submit because the build servers aren't
checkbuilding any 64-bit targets (aside from mips64, which is broken
for other reasons).

I've uploaded a build change to get treehugger building a 64-bit
target (http://cr/120564724), and also to make all the targets
checkbuilds again (http://cr/120568746).

Change-Id: I195000284de5b52a539a47ad8b308990e72eea96