chromium-x11: Add RDEPENDS on libx11-xcb.

[rakuco]

libX11-xcb.so.1 is loaded at runtime by the X11 backend, but we had no explicit dependency on the package that provides it (libx11-xcb).

It ended up being installed most of the time anyway, but make sure it is listed as a runtime dependency to avoid the issue described in #683.

Fixes #683.

Signed-off-by: Raphael Kubo da Costa raphael.kubo.da.costa@intel.com

[rakuco]

cc @MastaG @royaltm I haven't tested it myself, but @MastaG's suggestion makes sense given how the library is loaded at runtime.

[MastaG]

Lgtm2