EmulatorPkg: Add reference to new build instructions
Adds a reference to the new build instructions on the TianoCore wiki
that currently describe building with containers and Stuart.
Cc: Andrew Fish <afish@apple.com> Cc: Ray Ni <ray.ni@intel.com> Cc: Sean Brogan <sean.brogan@microsoft.com> Cc: Michael D Kinney <michael.d.kinney@intel.com> Cc: Liming Gao <gaoliming@byosoft.com.cn> Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com> Acked-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>