Fixes samples Teapot/MoreTeapots armeabi-v7a-hard; native-audio debug build

Fixes two issues:
1. Remove redundant check for hard-float in Teapot/MoreTeapots and ndk_helper
   they depend.  The ndk-build system add those flags already for armeabi-v7a-hard
2. native-audio in debug build: assert on the non-existance var

Change-Id: Id6b2d38a264c2f2d0e0c7fe625991fcee1762800
Merge "Fixes samples Teapot/MoreTeapots armeabi-v7a-hard; native-audio debug build"
auto-merger: merge in from aosp/master