Do not add bootstrap libs as providing from apex

Currently, com.android.runtime provides libc/libm/libdl to system. But
they are supposed to be used from symlinks under /system/lib not
directly from runtime apex.

This helps linkerconfig to generate ld.config.txt automatically for
apexes.

Bug: 144664390
Test: m com.android.runtime
      deapexer info com.android.runtime.apex

Change-Id: I1620e88e489fba88a06cc3bd6eb5b86a9b581e4f