lv2-postinst-helper.bbclass: Do not abort on failure but report error in postinstalllog

lv2-postinst-helper is last chance for plugins not working with qemu. So errors
are likely to happen. So it is better to have most plugins running and - more
important: avoid package-manager retry postinst every time some package is
installed.

Signed-off-by: Andreas Müller <schnitzeltony@gmail.com>

classes/lv2-postinst-helper.bbclass

@@ -35,7 +35,7 @@ pkg_postinst_ontarget_${PN}-lv2() {
     oldpath=`pwd`
     for sofile in `cat ${LV2-POSTINST-MANIFEST}`; do
         cd `dirname "$sofile"`
-        lv2-ttl-generator "$sofile"
+        lv2-ttl-generator "$sofile" || echo "Error: Turtle files for $sofile could not be created!"
     done
     cd $oldpath
 }