IntroduceRecCalls returns all calls. Adjust terminatingCalls.

src/main/scala/leon/grammars/SafeRecursiveCalls.scala

src/main/scala/leon/synthesis/Rules.scala

src/main/scala/leon/synthesis/rules/IntroduceRecCalls.scala

...n/scala/leon/synthesis/strategies/CostBasedStrategy.scala

src/main/scala/leon/synthesis/utils/Helpers.scala