Always use Java 21 for the Jenkins build

And use the toolchain for Java 17 and 11

Jenkinsfile

@@ -25,9 +25,9 @@ pipeline {
  }
 
  tools {
- // the Java version we use to run the build (minimal requirement for Maven/Tycho)
- // we force other Java versions through Maven toolchains
- jdk "temurin-jdk17-latest"
+ // the Java version we use to run the build
+ // we force the effective JDK version for compilation/testing through Maven toolchains
+ jdk "temurin-jdk21-latest"
  }
 
  stages {
@@ -68,6 +68,7 @@ pipeline {
  sh """
  ./full-build.sh --tp=${selectedTargetPlatform()} \
  ${javaVersion() == 11 ? '--toolchains releng/toolchains.xml -Pstrict-jdk-11' : ''} \
+ ${javaVersion() == 17 ? '--toolchains releng/toolchains.xml -Pstrict-jdk-17' : ''} \
  ${javaVersion() == 21 ? '-Pstrict-jdk-21' : ''}
  """
  }

pom.xml

@@ -445,8 +445,37 @@
  </plugins>
  </build>
  </profile>
+ <profile>
+ <id>strict-jdk-17</id>
+ <build>
+ <plugins>
+ <plugin>
+ <groupId>org.apache.maven.plugins</groupId>
+ <artifactId>maven-toolchains-plugin</artifactId>
+ <executions>
+ <execution>
+ <goals>
+ <goal>toolchain</goal>
+ </goals>
+ </execution>
+ </executions>
+ <configuration>
+ <toolchains>
+ <jdk>
+ <!-- Toolchain selected by maven/tycho-compiler for compilation and maven/tycho-surefire as JRE of launched test-runtimes-->
+ <version>17</version>
+ </jdk>
+ </toolchains>
+ </configuration>
+ </plugin>
+ </plugins>
+ </build>
+ </profile>
  <profile>
  <id>strict-jdk-21</id>
+ <!--
+ Here we don't use the toolchain relying on the effective Java version used for the build
+ -->
  <properties>
  <!--
  Since the Xtend compiler generates Java code using new API introduced in Java 21,