package/util-linux: build programs and libraries in separate packages

package/util-linux: build programs and libraries in separate packages

The findmount and lsblk utilities need udev to work correctly but cannot
be built with udev support because the packages providing libudev (eudev
and systemd) depend on util-linux, creating a chicken-egg problem. Solve
it by means of the following changes:

- Split util-linux into three packages:
  - util-linux-libs, providing lib{blkid,fdisk,mount,smartcols,uuid}.
  - util-linux-programs, providing both the aforementioned libs and the
    programs.
  - util-linux, a dummy package that drives configuration and building
    of the other ones.
- Add blind selections for -libs and -programs, i.e. they are indirectly
  selected according to the util-linux options.
- Make util-linux have build dependencies on util-linux-{libs,programs}
  if they are selected.
- host-util-linux has a build dependency on either host-util-linux-libs
  or host-util-linux-programs (not on both, since they are installed on
  the same destination).
- Make eudev and systemd have build dependencies on util-linux-libs.
  This can be extended to other packages in the future but is not needed
  right now because the configuration options are backward-compatible.
- Make util-linux-programs have an optional build dependency on the
  package that provides libudev (either eudev or systemd), if it is
  selected.

util-linux-libs is installed on STAGING_DIR by default and on TARGET_DIR
if util-linux-programs is not selected. Conversely, util-linux-programs
installs on TARGET_DIR by default and on STAGING_DIR if util-linux-libs
is not selected. This prevents installing the libraries twice on the
same destination, which would confuse check-uniq-files.

With this approach we don't need to patch configuration files neither
change other packages besides eudev and systemd. Other packages that
require util-linux libraries and whose libraries can be used by
util-linux programs can be updated later. We also don't need to change
any existing defcconfig, since all configuration options are kept in
the dummy util-linux package.

The main drawback of this approach is that util-linux-rebuild, as wel as
-reinstall, -reconfigure and even -dirclean targets do not have real
effect. It's necessary to use util-linux-libs-rebuild, for instance, but
this is a reasonable price to pay for the solution.

Fixes: https://bugs.busybox.net/show_bug.cgi?id=11811
Signed-off-by: Carlos Santos <unixmania@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>