Make libfstab available to APEXes.

The ART module needs this library to determine whether to put dexopt
artifacts in dalvik-cache.

Bug: 287958783
Test: m
(cherry picked from https://android-review.googlesource.com/q/commit:cf16f4d794a7162e6f418d2308741c6b45806f01)
Merged-In: Idf338702d4f54e9c40c0692ea29e7d83e91aca38
Change-Id: Idf338702d4f54e9c40c0692ea29e7d83e91aca38