Specify little-endian, and then use the “Standard size” from the chart. 

Enhance python tool.
The default being native size (and alignment) means by default the standard sizes are not used, which might cause different behavior on difference compiler.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: "Yao, Jiewen" <jiewen.yao@intel.com>
Reviewed-by: "Andrew Fish" <afish@apple.com>


git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16476 6f19259b-4bc3-4df7-8a09-765794883524