Statically link to libnativehelper

With ag/10113973, the check for apex_available property became correct.
However, in doing so, a bug in the apex mutator has revealed
(b/148645937). Due to the bug, libnativehelper.so wasn't copied into the
Bluetooth apk, because the lib is supposed  to be served from the ART
apex. However, there is no way for a apk in an APEX to use a native
lib from other APEX. Therefore, libnativehelper.so should actually be
copied into the Bluetooth apk.

Until the bug is fixed, make the linkage to libnativehelper as static so
that it is force included in the containing apk.

Exempt-From-Owner-Approval: cherry-pick from internal

Bug: 147671264
Test: m
Merged-In: Ia3c27416808bc9c53f4c501710cd4aaadfecbfe1
(cherry picked from commit 5459601c)
Change-Id: Ia3c27416808bc9c53f4c501710cd4aaadfecbfe1