Try this:
$ JAVA_OPTIONS="-XX:+CITime" ./ctw.sh test.jar

...and get no output. This is because internal tty shares the fd with System.out, which CTW runner closes on exit.

Bandaid fix:

diff -r 560b2becbe87 test/hotspot/jtreg/testlibrary/ctw/src/sun/hotspot/tools/ctw/CompileTheWorld.java
--- a/test/hotspot/jtreg/testlibrary/ctw/src/sun/hotspot/tools/ctw/CompileTheWorld.java Thu Jan 30 12:00:38 2020 -0800
+++ b/test/hotspot/jtreg/testlibrary/ctw/src/sun/hotspot/tools/ctw/CompileTheWorld.java Fri Jan 31 23:08:18 2020 +0100
@@ -97,13 +97,15 @@
                     System.currentTimeMillis() - start));
             passed = true;
         } catch (Throwable t){
             t.printStackTrace(ERR);
         } finally {
- try {
- OUT.close();
- } catch (Throwable ignore) {
+ if (OUT != System.out) {
+ try {
+ OUT.close();
+ } catch (Throwable ignore) {
+ }
             }
             // <clinit> might have started new threads
             System.exit(passed ? 0 : 1);
         }
     }