The latest hs-rt tree fails to build the Zero JVM variant. One issue affects all build types, release, fastdebug, slowdebug and concerns VM_Version:

hotspot/src/cpu/zero/vm/vm_version_zero.cpp:34:29: error: no ‘void VM_Version::initialize()’ member function declared in class ‘VM_Version’
 void VM_Version::initialize() {
                             ^
hotspot/make/linux/makefiles/rules.make:156: recipe for target 'vm_version_zero.o' failed
gmake[8]: *** [vm_version_zero.o] Error 1
gmake[7]: *** [the_vm] Error 2
gmake[6]: *** [productzero] Error 2
gmake[5]: *** [generic_buildzero] Error 2
gmake[4]: *** [productzero] Error 2


The other issue only surfaced for Zero release type build:

methodHandles_zero.o: In function `MethodHandles::method_handle_entry_linkToVirtual(Method*, long, Thread*)':
hotspot/src/cpu/zero/vm/methodHandles_zero.cpp:145: undefined reference to `oopDesc::klass() const'
methodHandles_zero.o: In function `MethodHandles::method_handle_entry_linkToInterface(Method*, long, Thread*)':
hotspot/src/cpu/zero/vm/methodHandles_zero.cpp:114: undefined reference to `oopDesc::klass() const'
hotspot/src/cpu/zero/vm/methodHandles_zero.cpp:121: undefined reference to `oopDesc::klass() const'
collect2: error: ld returned 1 exit status
hotspot/make/linux/makefiles/vm.make:335: recipe for target 'libjvm.so' failed
gmake[8]: *** [libjvm.so] Error 1
gmake[7]: *** [the_vm] Error 2