The following example fails on mac:
----------------------------------------
rm -rf output/simple* xxx foo

$JDK_HOME/bin/jpackage create-app-image \
--input input-hello \
--output output \
--name simple \
--main-jar hello.jar \
--main-class hello \
--temp-root foo \

rm -rf simple.app
cp -r output/simple.app .

$JDK_HOME/bin/jpackage create-installer \
--installer-type pkg \
--output output \
--app-image simple.app \
--name simple \
--verbose \
--temp-root xxx \
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if instead we put simple.app in a subdirectory (say my-simple) it works fine:
-------------------------------
$JDK_HOME/bin/jpackage create-installer \
--installer-type pkg \
--output output \
--app-image my-simple/simple.app \
--name simple \
--verbose \
--temp-root xxx \