Platform/Intel: Add Python build instructions

Updates ReadMe.md with the instructions for the Python build scripts.

Cc: Michael Kubacki <michael.a.kubacki@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Ankit Sinha <ankit.sinha@intel.com>

Signed-off-by: Agyeman <prince.agyeman@intel.com>
Reviewed-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
Reviewed-by: Michael Kubacki <michael.a.kubacki@intel.com>