user Makefiles: force remove files on clean

'make clean' twice in a row would cause an error trying to remove files
that don't exist.

Signed-off-by: Joel Nider <joel@nider.org>
root task: update include file name

The cpio code is now in cpio.h in the kernel.

Signed-off-by: Joel Nider <joel@nider.org>
gitignore: added *.service and *.driver

All userspace resulting files (drivers and services) should not be added to
git, and should not be seen by git.

Signed-off-by: Joel Nider <joel@nider.org>