chore: jlink improvements from jenkinsci/docker (#799)

alpine/Dockerfile

@@ -23,22 +23,21 @@ ARG JAVA_VERSION=17.0.10_7
 ARG ALPINE_TAG=3.19.1
 FROM eclipse-temurin:"${JAVA_VERSION}"-jdk-alpine AS jre-build
 
-RUN if [ "$TARGETPLATFORM" != 'linux/arm/v7' ]; then \
-    case "$(jlink --version 2>&1)" in \
+RUN case "$(jlink --version 2>&1)" in \
       # jlink version 11 has less features than JDK17+
-      "11."*) strip_java_debug_flags="--strip-debug" ;; \
-      *) strip_java_debug_flags="--strip-java-debug-attributes" ;; \
+      "11."*) set -- "--strip-debug" "--compress=2" ;; \
+      "17."*) set -- "--strip-java-debug-attributes" "--compress=2" ;; \
+      # the compression argument is different for JDK21
+      "21."*) set -- "--strip-java-debug-attributes" "--compress=zip-6" ;; \
+      *) echo "ERROR: unmanaged jlink version pattern" && exit 1 ;; \
     esac; \
     jlink \
+      "$1" \
+      "$2" \
       --add-modules ALL-MODULE-PATH \
-      "$strip_java_debug_flags" \
       --no-man-pages \
       --no-header-files \
-      --compress=2 \
-      --output /javaruntime; \
-  else \
-    cp -r /opt/java/openjdk /javaruntime; \
-  fi
+      --output /javaruntime
 
 ## Agent image target
 FROM alpine:"${ALPINE_TAG}" AS agent

debian/Dockerfile

@@ -32,22 +32,26 @@ SHELL ["/bin/bash","-e", "-u", "-o", "pipefail", "-c"]
 # Generate smaller java runtime without unneeded files
 # for now we include the full module path to maintain compatibility
 # while still saving space (approx 200mb from the full distribution)
-RUN if test "${TARGETPLATFORM}" != 'linux/arm/v7'; then \
-  case "$(jlink --version 2>&1)" in \
-    # jlink version 11 has less features than JDK17+
-    "11."*) strip_java_debug_flags=("--strip-debug") ;; \
-    *) strip_java_debug_flags=("--strip-java-debug-attributes") ;; \
-  esac; \
-  jlink \
-    --add-modules ALL-MODULE-PATH \
-    "${strip_java_debug_flags[@]}" \
-    --no-man-pages \
-    --no-header-files \
-    --compress=2 \
-    --output /javaruntime; \
-  # It is acceptable to have a larger image in arm/v7 (arm 32 bits) environment.
-  # Because jlink fails with the error "jmods: Value too large for defined data type" error.
-  else cp -r /opt/java/openjdk /javaruntime; \
+RUN if [[ "${TARGETPLATFORM}" != "linux/arm/v7" ]]; then \
+    case "$(jlink --version 2>&1)" in \
+      # jlink version 11 has less features than JDK17+
+      "11."*) set -- "--strip-debug" "--compress=2" ;; \
+      "17."*) set -- "--strip-java-debug-attributes" "--compress=2" ;; \
+      # the compression argument is different for JDK21
+      "21."*) set -- "--strip-java-debug-attributes" "--compress=zip-6" ;; \
+      *) echo "ERROR: unmanaged jlink version pattern" && exit 1 ;; \
+    esac; \
+    jlink \
+      "$1" \
+      "$2" \
+      --add-modules ALL-MODULE-PATH \
+      --no-man-pages \
+      --no-header-files \
+      --output /javaruntime; \
+  else \
+    # It is acceptable to have a larger image in arm/v7 (arm 32 bits) environment.
+    # Because jlink fails with the error "jmods: Value too large for defined data type" error.
+    cp -r /opt/java/openjdk /javaruntime; \
   fi
 
 ## Agent image target

debian/preview/Dockerfile

@@ -26,9 +26,9 @@ RUN set -x; apt-get update \
   && tar -xzf /tmp/jdk.tar.gz -C /opt/ \
   && rm -f /tmp/jdk.tar.gz
 
-ENV PATH=/opt/jdk-${JAVA_VERSION}/bin:$PATH
+ENV PATH="/opt/jdk-${JAVA_VERSION}/bin:${PATH}"
 
-RUN if test "${TARGETPLATFORM}" != 'linux/arm/v7'; then \
+RUN if [[ "${TARGETPLATFORM}" != "linux/arm/v7" ]]; then \
       jlink \
         --add-modules ALL-MODULE-PATH \
         --no-man-pages \