don't include liblog to APEXes

liblog is a platform library that provides stable C API. There is no
need to include the library, especialy by statically linking to it, in
any APEX. It not only wastes the storage/ram, but also is incorrect
because the socket interface to logd which is implemented in liblog is
not guaranteed to be stable.

Fixing this issue by converting static_libs: ["liblog"] into
shared_libs: ["liblog"], in which case the dependency to the library
is satisfied via the stub variant of the library.

Bug: 151051671
Test: m
Change-Id: I1573e2d7c3a79f27337dddf24c6e8d0c8189213f