tools/coreutils: disable uninstall target

tools/coreutils: disable uninstall target

GNU coreutils is a unique case where we require
some of the utilities on the host machine
before anything is built.

The prerequisite is handled by symlinks to the host binaries
in the staging directory that are installed
by the build system and that are expected to remain
as long as the corresponding stampfile exists.

Because the binaries built by coreutils
will replace the symlinks, the uninstall target
will actually delete the symlinks
long before the build finishes whenever it is ran.

This can cause the utilities to be temporarily missing
from the controlled part of the shell's PATH,
so disable the removal of the coreutils utilities.
The appropriate way to clear all of the programs and links
would be `make dirclean`.

Tested-by: Georgi Valkov <gvalkov@gmail.com> # macOS
Signed-off-by: Michael Pratt <mcpratt@pm.me>
Link: https://github.com/openwrt/openwrt/pull/16522
Signed-off-by: Robert Marko <robimarko@gmail.com>