BugLink: https://bugs.launchpad.net/bugs/1852637

Use dimlib.o (vs. dim.o) as the interim library object filename to avoid
a clash with the actual dim.c which manifests as:

make[2]: Circular lib/dim/dim.o <- lib/dim/dim.o dependency dropped.
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Acked-by: Khaled Elmously <khalid.elmously@canonical.com>
Acked-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>