Fix Mac ndk-build error on motive, pie_noon, pindrop.

We were looking for 'flatc' in motive/bin/Debug/flatc,
on Mac. It's actually built to flatbuffers/Debug/flatc.

Tested: OS X Yosemite, ndk-r10d. Also tested on Linux.
Change-Id: I9f1ecfe00c5f42fd9b6808b5a5da1c920487a4c2
2 files changed