After "8345655: Move reservation code out of ReservedSpace" the AIX fastdebug build fails with

/priv/jenkins/client-home/workspace/openjdk-jdk-dev-aix_ppc64-dbg/jdk/src/hotspot/share/memory/memoryReserver.cpp:513:26: error: incomplete type 'os::Aix' named in nested name specifier
        AIX_ONLY(&& (os::Aix::supports_64K_mmap_pages() || os::vm_page_size() == 4*K))) {
                     ~~~~^~~~~
/priv/jenkins/client-home/workspace/openjdk-jdk-dev-aix_ppc64-dbg/jdk/src/hotspot/share/utilities/macros.hpp:399:24: note: expanded from macro 'AIX_ONLY'
#define AIX_ONLY(code) code
                       ^~~~
/priv/jenkins/client-home/workspace/openjdk-jdk-dev-aix_ppc64-dbg/jdk/src/hotspot/share/runtime/os.hpp:1024:9: note: forward declaration of 'os::Aix'
  class Aix;