Fix SecurityPkg build breaks for ARM and RISCV64 by adding RngLib mapping. Cc: Jiewen Yao <jiewen.yao@intel.com> Cc: Jian J Wang <jian.j.wang@intel.com> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org> Cc: Abner Chang <abner.chang@hpe.com> Cc: Daniel Schaefer <daniel.schaefer@hpe.com> Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com> Acked-by: Jiewen Yao <Jiewen.yao@intel.com> Acked-by: Abner Chang <abner.chang@hpe.com> Reviewed-by: Daniel Schaefer <daniel.schaefer@hpe.com>