net-im/twinkle-0.3.2 doesn't require aRts to be built and/or used. I suggest adding an 'arts' USE flag to the ebuild to enable the user to select usage of aRts. I will add a patch for this ebuild, which adds an arts USE flag and uses it during configuration. Reproducible: Always Steps to Reproduce:
Created attachment 72624 [details, diff] patch to net-im/twinke-0.3.2 to add an arts USE flag
added to 0.3.2-r1 thanks Felix