x11vnc: remove redundant RPATH to fix QA issue

The useless rpath caused oe QA issue:
...
|ERROR: QA Issue: x11vnc: work/i586-poky-linux/x11vnc/0.9.13-r0/packages-split/
x11vnc/usr/bin/x11vnc contains probably-redundant RPATH /usr/lib [useless-rpaths]
...

In oe build, it is unnecessary and redundant to pass "-R/usr/lib" to the linker.

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
(cherry picked from commit d209e32ffbcbbf419c3b5677777ac2e244bcebc1)
Signed-off-by: Armin Kuster <akuster808@gmail.com>