build: lock versions for special APK packages

build: lock versions for special APK packages

The three packages base-files, libc and kernel are special, the former
can't be upgraded in place since it's content are modified on startup,
the latter two are virtual packages only used as constraints for the
package manager.

Historically base-files was "locked" via a special OPKG function, the
latter two were hidden from the package index and thereby never picked
as possible upgrade.

Time moved forward and we now have APK and tools like OWUT. The latter
compares available packages with installed packages and generates user
readable output, requiring versions for libc and kernel, too. At the
same time, APK uses a different looking mechanism, which is set during
installation instead of part of the package metadata.

In short, this patch adds version constraints to the three packages,
allowing them to be part of the package index.

Fixes: #17774
Fixes: #17775
Fixes: efahl/owut#31
Signed-off-by: Paul Spooren <mail@aparcar.org>