cmake: use property list for GPU_TARGETS

This PR deprecates the variable `AMDGPU_TARGETS`.
To choose architectures it is required to set `GPU_TARGETS`.
Before this PR `GPU_TARGETS` was set to `AMDGPU_TARGETS`.
Calling `cmake` again with a new value for `AMDGPU_TARGETS` is not propagated to `GPU_TARGETS` therefore the user is building against the initially selected architecture which is not obvious.

This PR
  - If the user is setting `AMD_GPU_TARGETS` in the **initial cmake call** e.g. `cmake -DAMDGPU_TARGETS=gfx908` a deprecation warning is thrown and the value of `AMDGPU_TARGETS` is assigned to `GPU_TARGETS`
  - `GPU_TARGETS` can be any time overwritten by a user-defined value which allows an expert user to select architecture features too, e.g. `cmake -DGPU_TARGETS=gfx908:xnack+`

Co-authored-by: Paul Fultz II <[email protected]>

Author: psychocoderHPC

hip-config.cmake.in

@@ -159,8 +159,14 @@ if(HIP_COMPILER STREQUAL "clang")
   if(NOT WIN32)
     find_dependency(AMDDeviceLibs)
   endif()
-  set(AMDGPU_TARGETS "gfx900;gfx906;gfx908;gfx90a;gfx1030" CACHE STRING "AMD GPU targets to compile for")
-  set(GPU_TARGETS "${AMDGPU_TARGETS}" CACHE STRING "GPU targets to compile for")
+  set(GPU_DEFAULT_TARGETS "gfx900;gfx906;gfx908")
+
+  if(NOT DEFINED AMDGPU_TARGETS)
+      set(GPU_TARGETS "${GPU_DEFAULT_TARGETS}" CACHE STRING "GPU targets to compile for. Adding features is supported e.g. gfx908:xnack+")
+  else()
+      message(WARNING "Variable AMDGPU_TARGETS is deprecated! Please use GPU_TARGETS to choose architectures.")
+      set(GPU_TARGETS "${AMDGPU_TARGETS}" CACHE STRING "GPU targets to compile for. Adding features is supported e.g. gfx908:xnack+")
+  endif()
 endif()
 
 if(NOT WIN32)