Bug#28730189 wrong rpath for router on solaris

On solaris absolute, hardcoded rpaths were used. As the location
of the libraries changed from /opt/mysql/mysql-router to
/opt/mysql/mysql libraries weren't found at startup.

Instead of using absolute paths, relative rpaths are used by using
$ORIGIN on Solaris too.

router/cmake/set_rpath.cmake

@@ -82,7 +82,7 @@ ENDIF()
 
 SET(CMAKE_INSTALL_RPATH)
 IF(INSTALL_LAYOUT STREQUAL "STANDALONE" OR INSTALL_LAYOUT STREQUAL "DEFAULT" OR
-   INSTALL_LAYOUT STREQUAL "WIN")
+   INSTALL_LAYOUT STREQUAL "WIN" OR INSTALL_LAYOUT STREQUAL "SVR4")
   # rpath for lib/mysqlrouter/ plugins that want to find lib/
   SET(RPATH_PLUGIN_TO_LIB "${RPATH_ORIGIN}/../")
   SET(RPATH_PLUGIN_TO_PLUGIN "${RPATH_ORIGIN}/")
@@ -92,11 +92,7 @@ IF(INSTALL_LAYOUT STREQUAL "STANDALONE" OR INSTALL_LAYOUT STREQUAL "DEFAULT" OR
   SET(RPATH_BINARY_TO_LIB "${RPATH_ORIGIN}/../${ROUTER_INSTALL_LIBDIR}/")
 
 ELSE()
-  IF(INSTALL_LAYOUT STREQUAL "SVR4")
-    SET(_dest_dir "/opt/mysql/mysql-router/")
-  ELSE()
-    SET(_dest_dir "${CMAKE_INSTALL_PREFIX}")
-  ENDIF()
+  SET(_dest_dir "${CMAKE_INSTALL_PREFIX}")
   # rpath for lib/mysqlrouter/ plugins that want to find lib/
   SET(RPATH_PLUGIN_TO_LIB "${_dest_dir}/${ROUTER_INSTALL_LIBDIR}")
   SET(RPATH_PLUGIN_TO_PLUGIN "${_dest_dir}/${ROUTER_INSTALL_PLUGINDIR}")