tools/misc: Cleanup makefile

tools/misc: Cleanup makefile

The existing makefile was awkward with needing to express conditional
inclusion for both the build and install rules, and contained both split and
unsplit long lines.

The INSTALL_* rules now contain the conditional inclusion information, while
the TARGET_* rules generate the build list from the complete install list,
less the minority of scripts which simply need copying into place.  Comments
are introduces to aid clarity.

In addition, collect the CFLAGS expressions, remove the unreferenced and empty
HDRS list, and restrict the libxc internals build fix to the offending
binaries.

No functional change as a result of this patch, but it is rather more simple
to add or remove utilities.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Ian Campbell <Ian.Campbell@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>