Loading JNI libraries in an APEX

It's a cherry-pick from aosp/master https://r.android.com/1247869,
because this change is skipped when merging from rvc-dev-plus-aosp
http://ag/10495311, which specifies "DO NOT MERGE" in its commit
message.

To load JNI libraries in an APEX, libnativeloader relies on
jni.config.txt file which contains available JNI libraries for
APEX namespaces:

  com_android_foo libfoo_jni.so:...
  com_android_bar libbar_jni.so:...

This file is generated by linkerconfig.

Bug: 143733063
Test: cuttlestone boots
      (For now, no behavioral changes because jni.config.txt is empty)
Change-Id: I066de90a73875118be53972e50d076061922d762
(cherry picked from commit 538f99ab285c1440969b9b3331fc0ce750c0d316)
6 files changed