How can I use RSVG with ImageMagick?
This message indicates that cairo, a prerequisite for librsvg, cannot find the configuration options for package xcb-shm. They should be stored in /opt/X11/lib/pkgconfig/xcb-shm.pc. All you have to do is add this path to the environment variable $PKG_CONFIG_PATH:

export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/opt/X11/lib/pkgconfig


configure should now be able to find what it is looking for.