make DESTDIR=/home/dj/stage prefix=/rbtree-1.0.9 exec_prefix=/rbtree-1.0.9/x86
install
The resultant file hierarchy is shallower:
/home/dj/stage
/home/dj/stage/rbtree-1.0.9
/home/dj/stage/rbtree-1.0.9/x86
/home/dj/stage/rbtree-1.0.9/x86/lib
/home/dj/stage/rbtree-1.0.9/x86/lib/pkgconfig
/home/dj/stage/rbtree-1.0.9/include
/home/dj/stage/rbtree-1.0.9/include/rbtree
and works well with the graft program.
In the context of my original question vis-a-vis libtool, I've been
using this approach for many years with a large number of distributions
which use libtool and have never had libtool refuse to install a library
into the staging area.