Lanai: a lot of crashes at [libdispatch.dylib+0x4769] _dispatch_assert_queue_fail+0x63

(from https://youtrack.jetbrains.com/issue/JBR-1988 )

A lot of tests crash on `Lanai` builds with the following output:

#section:main
----------messages:(5/199)----------
command: main UnfocusableToplevel
reason: User specified action: run main UnfocusableToplevel
Mode: othervm
Additional options from @modules: --add-modules java.desktop
elapsed time (seconds): 2.09
----------configuration:(3/40)----------
Boot Layer
  add modules: java.desktop

----------System.out:(20/942)----------
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGILL (0x4) at pc=0x00007fff693c6769, pid=36139, tid=25347
#
# JRE version: OpenJDK Runtime Environment (14.0+9) (build 14+9-blanai.4)
# Java VM: OpenJDK 64-Bit Server VM (14+9-blanai.4, mixed mode, sharing, tiered, compressed oops, g1 gc, bsd-amd64)
# Problematic frame:
# C [libdispatch.dylib+0x4769] _dispatch_assert_queue_fail+0x63
#
# No core dump will be written. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /Users/builduser/teamcity-agent/work/752ef37498e1f52c/JTwork/scratch/hs_err_pid36139.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#

Steps to reproduce:
$ jtreg -testjdk:[path_to_lanai_build] test/jdk/java/awt/Choice/UnfocusableToplevel/UnfocusableToplevel.java