Remove ndk_platform backend. Use the ndk backend.

The ndk_platform backend will soon be deprecated because the ndk backend
can serve the same purpose. This is to eliminate the confusion about
having two variants (ndk and ndk_platform) for the same ndk backend.

Bug: 161456198
Test: m
Merged-In: I9343e1bdc1ec05b4d0deced840ea861897f82659
Change-Id: I9343e1bdc1ec05b4d0deced840ea861897f82659
(cherry picked from commit 734d0a438cc76948fcf94d4353c7b3b444e320c3)
1 file changed