build.dir not based on configure.dir

[Ryan Schmidt]

from portconfigure.tcl:

default configure.dir       {${worksrcpath}}


from portbuild.tcl:

default build.dir {${workpath}/${worksrcdir}}


from portdestroot.tcl:

default destroot.dir {${build.dir}}



So destroot.dir is based on build.dir but build.dir isn't based on  
configure.dir. Why not? It means that if a port wants to override the  
configure/build/destroot directory it has to set both the  
configure.dir and the build.dir. Wouldn't it be nice if it could just  
set the configure.dir and the others would inherit the new value?