tools: fix python install with "xentoollog"

commit 5d3dc86715
"tools: Refactor "xentoollog" into its own library"
with older python versions (2.6.4) will fail to
the build if attempted to be done twice (which
happens due to pygrub dependencies).

make -C python DESTDIR=/tmp
make -C python DESTDIR=/tmp

The second one will fail with:
error: -Wl, -rpath-link=../../tools/libs/toollog: No such file or directory

even though the directory is there (with the libs).

Andrew pointed out that the linker additions should be in
the "extra_link_args" rather than "depends".

And true enough - with that modification it builds.

CC: Ian Campbell <ian.campbell@citrix.com>
CC: Ian Jackson <ian.jackson@eu.citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Suggested-by: Andrew Cooper <andrew.cooper3@citirx.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
[ ijc -- typo in commit message ]

tools/python/setup.py

@@ -17,7 +17,8 @@ xc = Extension("xc",
                include_dirs       = [ PATH_XEN, PATH_LIBXENTOOLLOG + "/include", PATH_LIBXC + "/include", "xen/lowlevel/xc" ],
                library_dirs       = [ PATH_LIBXC ],
                libraries          = [ "xenctrl", "xenguest" ],
-               depends            = [ PATH_LIBXC + "/libxenctrl.so", PATH_LIBXC + "/libxenguest.so",  "-Wl,-rpath-link="+PATH_LIBXENTOOLLOG ],
+               depends            = [ PATH_LIBXC + "/libxenctrl.so", PATH_LIBXC + "/libxenguest.so" ],
+               extra_link_args    = [ "-Wl,-rpath-link="+PATH_LIBXENTOOLLOG ],
                sources            = [ "xen/lowlevel/xc/xc.c" ])
 
 xs = Extension("xs",