rocmPackages.composable_kernel: fix gfx906 only failure (#495648)

  rocmUpdateScript,

  cmake,

  rocm-cmake,

  llvm,

  clr,

  rocminfo,

  python3,

    "-DGOOGLETEST_DIR=${gtest.src}" # Custom linker names

  ];

  # No flags to build selectively it seems...

  patches = [

    # Hacky fix for failure for some targets when all targets are selected out

    # for a non-optional at link time kernel

    ./fix-empty-offload-targets.diff

  ];

  postPatch =

    # Reduce configure time by preventing thousands of clang-tidy targets being added

    # We will never call them

diff --git a/library/src/tensor_operation_instance/gpu/CMakeLists.txt b/library/src/tensor_operation_instance/gpu/CMakeLists.txt

index 172f6681b8..d3ddbb2f15 100644

--- a/library/src/tensor_operation_instance/gpu/CMakeLists.txt

+++ b/library/src/tensor_operation_instance/gpu/CMakeLists.txt

@@ -154,9 +154,15 @@ function(add_instance_library INSTANCE_NAME)

                 list(FILTER INST_TARGETS INCLUDE REGEX "gfx12")

             endif()

             set(offload_targets)

-            foreach(target IN LISTS INST_TARGETS)

-                string(APPEND offload_targets "--offload-arch=${target} ")

-            endforeach()

+            if(NOT INST_TARGETS)

+                # No valid GPU targets for this source, compile for 90a as fallback

+                # so the add_device…instances and hip_fatbin… symbols still exist

+                set(offload_targets "--offload-arch=gfx90a")

+            else()

+                foreach(target IN LISTS INST_TARGETS)

+                    string(APPEND offload_targets "--offload-arch=${target} ")

+                endforeach()

+            endif()

             set_source_files_properties(${source} PROPERTIES COMPILE_FLAGS ${offload_targets})

             list(APPEND INST_OBJ ${source})

         endforeach()