Update Krill Java version

Change-Id: I9e57377f6d93661e39443c8ff3607e52d08cc416
diff --git a/bin/git_gerrit_pull b/bin/git_gerrit_pull
index bb4b6c8..ae1e7b1 100755
--- a/bin/git_gerrit_pull
+++ b/bin/git_gerrit_pull
@@ -9,11 +9,17 @@
 my $JAVA8_HOME  = '/usr/lib/jvm/java-1.8.0-openjdk-amd64';
 my $JAVA11_HOME = '/usr/lib/jvm/java-1.11.0-openjdk-amd64';
 my $JAVA17_HOME = '/usr/lib/jvm/java-1.17.0-openjdk-amd64';
+my $JAVA21_HOME = '/usr/lib/jvm/java-1.21.0-openjdk-amd64';
 
 unless (-d $JAVA17_HOME) {
   $JAVA17_HOME = '/opt/java/jdk-17.0.2';
 };
 
+unless (-d $JAVA21_HOME) {
+  $JAVA21_HOME = '/opt/java/jdk-21.0.0';
+};
+
+
 my $url = $ARGV[0];
 
 sub _check {
@@ -74,7 +80,7 @@
 
 # Krill
 elsif ($project =~ m!^Krill$!i) {
-  _check('JAVA_HOME="'.$JAVA17_HOME.'" mvn clean test');
+  _check('JAVA_HOME="'.$JAVA21_HOME.'" mvn clean test');
 }
 
 # Kalamar-Plugin-ExternalResources