RuntimeHintsAgentPlugin purpose is to verify that the reflective
invocations expected match the ones performed.
gh-30242 introduces a code path where the reflective invocation
is skipped when running on native.
This issue set the system property "org.graalvm.nativeimage.imagecode"
to "runtime" when running runtime tests with the agent in order to
make sure the code path tested for those tests is the native one.
Closes gh-30422
f469eff97b