Add libdl_android as a bootstrap library.

Necessary after moving it into the Runtime APEX, as several framework
libraries loaded during early boot depends on it, e.g. libvndksupport.so,
libvulkan.so, and libgraphicsenv.so.

Test: build & boot
Bug: 135753770
Change-Id: I5862ba57485bdaffd452aac47c5931863823075d