core/jenkins-toolchains.xml

<?xml version="1.0" encoding="UTF-8"?>
<toolchains>
  <!-- From our maven:3.6.1-jdk-8 Docker image -->
  <toolchain>
    <type>jdk</type>
    <provides><id>JavaSE-1.8</id></provides>
    <configuration><jdkHome>/usr/local/openjdk-8</jdkHome></configuration>
  </toolchain>
</toolchains>