xed_mbuild.py: now that using wkit build, do not require "install" when using "doc" target
xed_mbuild.py: now that using wkit build, do not require "install" when using "doc" target

Change-Id: I0a59b037433cd8ddc01aad943fd09c78886aa9c4
(cherry picked from commit a0ee5267418db098017462c7b19ca4fe7f09017d)

intelxed/xed,intelxed/xed,intelxed/xed,intelxed/xed