$ rm -rf jdk-jimage
$ ./build/macosx-x64/images/jdk/bin/java -version
java version "18-internal" 2022-03-15
Java(TM) SE Runtime Environment (build 18-internal+0-2021-08-18-2003055.shura...)
Java HotSpot(TM) 64-Bit Server VM (build 18-internal+0-2021-08-18-2003055.shura..., mixed mode, sharing)
$ ./build/macosx-x64/images/jdk/bin/jlink --add-modules java.base,java.compiler --output jdk-jimage
$ ./jdk-jimage/bin/java -version
java version "18-internal" 2022-03-15
Java(TM) SE Runtime Environment (build 18-internal+0-2021-08-18-2003055.shura...)
Java HotSpot(TM) 64-Bit Server VM (build 18-internal+0-2021-08-18-2003055.shura..., mixed mode)
$ java -jar jcov_3.0/jcov.jar JREInstr -implantrt jcov_3.0/jcov_network_saver.jar jdk-jimage
Command line error: bootmodules.jimage was not found in modules directory

Use "java -jar jcov.jar JREInstr -h" for command-line help or "java -jar jcov.jar JREInstr -hv" for wider description
$ ls -l jdk-jimage//lib/modules
-rw-r--r-- 1 shura staff 24704386 Aug 20 13:54 jdk-jimage//lib/modules