Make apex availability of fmtlib_ndk explicit am: 9ceaceb712 am: 6e91310212

Original change: https://android-review.googlesource.com/c/platform/external/fmtlib/+/2894402

Change-Id: I06125f2da463eea322d51923f0e50c66bac54293
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>