[libomptarget] Build amdgpu plugin by default

[JonChesterfield]

Summary

[libomptarget] Build amdgpu plugin by default

This will build the amdgpu plugin if cmake is able to find the hsa
runtime library, which will be the case if rocm is installed or if
the hsa library has been installed somewhere cmake looks.

[tianshilei1992]

LG.

openmp/libomptarget/plugins/CMakeLists.txt

else(LIBOMPTARGET_DEP_LIBELF_FOUND)
     libomptarget_say("Not building ${tmachine_name} offloading plugin: libelf dependency not found.")
   endif(LIBOMPTARGET_DEP_LIBELF_FOUND)
 else()
   libomptarget_say("Not building ${tmachine_name} offloading plugin: machine not found in the system.")
 endif()
 endmacro()
 
 add_subdirectory(aarch64)
+add_subdirectory(amdgpu)
 add_subdirectory(cuda)
 add_subdirectory(ppc64)
 add_subdirectory(ppc64le)
 add_subdirectory(ve)
 add_subdirectory(x86_64)
 add_subdirectory(remote)
 
 # Make sure the parent scope can see the plugins that will be created.
 set(LIBOMPTARGET_SYSTEM_TARGETS "${LIBOMPTARGET_SYSTEM_TARGETS}" PARENT_SCOPE)
 set(LIBOMPTARGET_TESTED_PLUGINS "${LIBOMPTARGET_TESTED_PLUGINS}" PARENT_SCOPE)