Install bootstrap variant of bionic libs

Bionic libs are moved to the runtime APEX and thus are available via the
path /apex/com.android.runtime/lib[64]. However, for processes that are
started before the APEX is ready, a copy of the bionic libs should be left
under /system/lib[64]. This change ensures that the bootstrap bionic
libs are always installed to the system partition.

Note that, at runtime, the bionic libs in the runtime APEX are
bind-mounted to /system/lib/<libname>.so which essentially hides the
bootstrap bionic libs to the processes after the activation of the
runtime APEX.

Bug: 120266448
Test: m and check that libc, libdl, libm are under
/system/lib[64]

Change-Id: I9d5e8e718aa020c012f312a70ed54652130048dd