Converts benchmark JNI lib to NDK (*.mk) build to support older SDKs.

Bug: 120554763

Test: Ran com.android.nn.benchmark.app.NNTest on walleye-userdebug and blueline-userdebug
Change-Id: I837da0a56f1f1bc6270fc91b32ba26efd53fa90d
Merged-In: I837da0a56f1f1bc6270fc91b32ba26efd53fa90d
(cherry picked from commit d0b056f01bb9d53703d9b304791e38d39543ef2d)
7 files changed