bumped bytecode level of jdk12+ profile to 8
    
    it is not enough:
    [ERROR] /builddir/build/BUILD/jacoco-0.8.10/jacoco-maven-plugin/src/org/jacoco/maven/MergeMojo.java:[89,80] incompatible types: org.apache.maven.plugin.logging.Log cannot be converted to org.slf4j.Logger
    [INFO] 1 error
    [INFO] --------------