MySQL uses two source layouts when building : the bzr 
layout and the source package layout.
The previous fix for bug 35250 contained 1 change that is
valid for both modes and a number of changes that are valid
only for the bzr source layout.
The important thing was to fix the source package layout.
And for this the change in configure.in was sufficient.
It's not trivial (and not requested by this bug) to support 
VPATH builds from the bzr trees.
This is why the other changes are reverted and the change to
fix the VPATH build for source distributions is left intact.