We attached the JSON flag to the wrong AST node, causing Docker to treat
the exec form ["binary", "arg"] as if the shell form "binary arg" had
been used. This failed if "ls" was not present.
Added a test to detect this.
Fixes#26174
Signed-off-by: Thomas Leonard <thomas.leonard@docker.com>
(cherry picked from commit e95b6b51da)
Signed-off-by: Victor Vieux <vieux@docker.com>