tools: Introduce $(xenlibs-rpath,..) to replace $(SHDEPS_lib*)

tools: Introduce $(xenlibs-rpath,..) to replace $(SHDEPS_lib*)

This patch introduce a new macro $(xenlibs-dependencies,) to generate
a list of all the xen library that a library is list against, and they
are listed only once. We use the side effect of $(sort ) which remove
duplicates.

This is used by another macro $(xenlibs-rpath,) which is to replace
$(SHDEPS_libxen*).

In libs.mk, we don't need to $(sort ) SHLIB_lib* anymore as this was used
to remove duplicates and they are no more duplicates.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>