futher help Gradle finding installed JDKs

Author: ktoso

.github/actions/prepare_env/action.yml

@@ -14,10 +14,13 @@ runs:
         cache: 'gradle'
     - name: Re-export JAVA_HOME
       run: >
-        if [[ -n "$JAVA_HOME_24_ARM64" ]]; then echo "JAVA_HOME_24=${{ env.JAVA_HOME_24_ARM64 }}" >> $GITHUB_ENV; fi;
-        if [[ -n "$JAVA_HOME_24_X64" ]]; then echo "JAVA_HOME_24=${{ env.JAVA_HOME_24_X64 }}" >> $GITHUB_ENV; fi;
-        if [[ -n "$JAVA_HOME_21_ARM64" ]]; then echo "JAVA_HOME_21=${{ env.JAVA_HOME_21_ARM64 }}" >> $GITHUB_ENV; fi;
-        if [[ -n "$JAVA_HOME_21_X64" ]]; then echo "JAVA_HOME_21=${{ env.JAVA_HOME_21_X64 }}" >> $GITHUB_ENV; fi;
+        # Gradle specifically looks for JDK_N environment variables to detect installed JDK versions,
+        # so we need to ensure it can find it, so it picks up JDK_24 since we are using 21 for Gradle itself,
+        # because it does not (yet) support JDK 24+. If it did, we wouldn't need multiple JDKs installed.
+        if [[ -n "$JAVA_HOME_24_ARM64" ]]; then echo "JDK_24=${{ env.JAVA_HOME_24_ARM64 }}" >> $GITHUB_ENV; fi;
+        if [[ -n "$JAVA_HOME_24_X64" ]]; then echo "JDK_24=${{ env.JAVA_HOME_24_X64 }}" >> $GITHUB_ENV; fi;
+        if [[ -n "$JAVA_HOME_21_ARM64" ]]; then echo "JDK_21=${{ env.JAVA_HOME_21_ARM64 }}" >> $GITHUB_ENV; fi;
+        if [[ -n "$JAVA_HOME_21_X64" ]]; then echo "JDK_21=${{ env.JAVA_HOME_21_X64 }}" >> $GITHUB_ENV; fi;
       shell: bash
     - name: List JAVA_HOME
       run: env | grep JAVA_HOME