extensions: export content snap egl vendor dir (#3190)

Also remove conditional check on the "base" vendor directory as
append_dir already takes care of directory existence.

Signed-off-by: Sergio Schvezov <sergio.schvezov@canonical.com>
Co-authored-by: Ken VanDine <ken.vandine@canonical.com>

Co-authored-by: Ken VanDine <ken.vandine@canonical.com>

extensions/desktop/common/desktop-exports

@@ -99,8 +99,8 @@ append_dir LD_LIBRARY_PATH "$SNAP_DESKTOP_RUNTIME/usr/lib/$ARCH/libunity"
 append_dir LD_LIBRARY_PATH "$SNAP_DESKTOP_RUNTIME/usr/lib/$ARCH/pulseaudio"
 
 # EGL vendor files on glvnd enabled systems
-[ -d /var/lib/snapd/lib/glvnd/egl_vendor.d ] && \
-    append_dir __EGL_VENDOR_LIBRARY_DIRS "/var/lib/snapd/lib/glvnd/egl_vendor.d"
+append_dir __EGL_VENDOR_LIBRARY_DIRS "/var/lib/snapd/lib/glvnd/egl_vendor.d"
+append_dir __EGL_VENDOR_LIBRARY_DIRS "$SNAP_DESKTOP_RUNTIME/usr/share/glvnd/egl_vendor.d"
 
 # Tell GStreamer where to find its plugins
 export GST_PLUGIN_PATH="$SNAP/usr/lib/$ARCH/gstreamer-1.0"