[OPENJDK-2736] jlink pre-flight check for jmods

Fail early and clearly if we don't have the jmods available for
Jlink integration (or the JDK version isn't right)

https://issues.redhat.com/browse/OPENJDK-2736

Signed-off-by: Jonathan Dowland <[email protected]>

Author: jmtd

modules/jlink/artifacts/opt/jboss/container/java/jlink/preflight.sh

@@ -0,0 +1,12 @@
+jlink_preflight_check()
+{
+    # preflight check: do we have what we need?
+    if [ "$JAVA_VERSION" -lt 11 ]; then
+      echo "Jlink integration not available for JDK${JAVA_VERSION}!"
+      echo "Jlink integration is only supported for JDK versions 11 and newer."
+    fi
+    if [ ! -d /usr/lib/jvm/java/jmods ]; then
+      echo "Jlink integration requires the jmods RPM to be installed in the builder image, e.g."
+      echo "        microdnf install -y java-${JAVA_VERSION}-openjdk-jmods"
+    fi
+}

modules/s2i/bash/artifacts/usr/local/s2i/assemble

@@ -21,6 +21,9 @@ setup_java_app_and_lib
 # include our jlink scripts
 if [ "$S2I_ENABLE_JLINK" = "true" ]; then
 
+    source "${JBOSS_CONTAINER_JAVA_JLINK_MODULE}/preflight.sh"
+    jlink_preflight_check
+
     source "${JBOSS_CONTAINER_JAVA_JLINK_MODULE}/mkdeps.sh"
     echo "Invoking mkdeps"
     generate_deps