Adapt to rearranged NDK sysroot.

Soong didn't have any explicit references to these paths because it
depends directly on the modules, but the make side of the build still
needs to construct these paths explicitly.

I removed a bunch of dead code that made the fix less obvious while I
was here.

Bug: None
Test: treehugger
Change-Id: I1a283a3bc98a94fc5481c869b3b0a4eacf69d859