debian: look for quota.pc and libquota.a from root of install tree

debian: look for quota.pc and libquota.a from root of install tree

The rules makefile was already using `find' in order to cope with
multi-arch directories under /usr/lib. This patch changes it to look for
those files from the root of the install tree. This allows for
installing to libdirs of /usr/lib64 or /lib or /lib64. There are no
other files with the same names in the package so it's not a problem to
find from the root of the tree.

Signed-off-by: Filipe Brandenburger <filbranden@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>