possible problem with $(dir ... )

[Warren Dodge]

I notice that $(dir ...) leaves the trailing / when given a full
filename path.

Is there an easy way to remove the trailing / ?

It would nice to have a function that didn't leave it there in some
applications we have. 

I tried to do this so I could get the root dir of a program, but it
fails to give me /x/y/z and gives /x/y/z/bin/ . I assume the trailing /
in /x/y/z/bin/ is the problem.

$(dir $(dir  /x/y/z/bin/program))

I was trying to avoid using $(shell ... ) which I assume is slower.