build: add rpath to modules that use symbols from libexec_weston

The cms-static, desktop-shell, hmi-controller, ivi-shell, and screen-share modules use symbols from libexec_weston, e.g.:

$ ldd /usr/lib/x86_64-linux-gnu/weston/desktop-shell.so | grep "not found" libexec_weston.so.0 => not found

Loading these modules from weston happens to work because the weston executable itself links against libexec_weston, and has an rpath set. Still, these modules depend on a library in a non-standard location. Adding an rpath could help static checkers to make sure all shared objects' dependencies are present.

Signed-off-by: Philipp Zabel p.zabel@pengutronix.de