When Graal is built as part of JDK it requires first to build an annotation processor using boot jdk 8.
After JDK-8167180 changes Services class is used by annotation processor but the code is using jdk 9 Module API and it can't be compiled with jdk 8:

hotspot/src/jdk.vm.ci/share/classes/jdk.vm.ci.services/src/jdk/vm/ci/services/Services.java:25: error: cannot find symbol
import java.lang.reflect.Module;
                        ^
  symbol: class Module
  location: package java.lang.reflect
hotspot/src/jdk.vm.ci/share/classes/jdk.vm.ci.services/src/jdk/vm/ci/services/Services.java:55: error: cannot find symbol
        Module jvmci = Services.class.getModule();
        ^
  symbol: class Module
  location: class Services
hotspot/src/jdk.vm.ci/share/classes/jdk.vm.ci.services/src/jdk/vm/ci/services/Services.java:55: error: cannot find symbol
        Module jvmci = Services.class.getModule();
                                     ^
  symbol: method getModule()
  location: variable class of type Class<Services>


Use reflection instead of Module API.