Makefile: hide commands that build the package file lists at end of build

Since commit 0e2be4db
("package/pkg-generic: make file list logic parallel build
compatible"), the commands executed at the every end of the build
to assemble the list of files installed by the different packages
are visible in the make output. They are quite noisy, and clutter
the output.

The other commands in target-finalize are also hidden using "@",
so we should also do the same for those commands. But that hurts
debuggability, so we use $(Q) (the existing '@'s can be changed
in a followup patch).

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
[yann.morin.1998@free.fr: use '$(Q)', not '@']
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>