Merge pull request #14655 from dotty-staging/fix-java8-ci

Fix the Java 8 CI

Author: smarter

tests/disabled/pos/i12956.java

@@ -0,0 +1,5 @@
+// Disable because it requires Java 9+ but our CI still runs on Java 8 and our
+// testing infrastructure doesn't let us run a test only on Java 9+.
+interface Foo {
+  private void bar() {}
+}