This is not needed. Gentoo automatically collect license files into
the documentation directory.

Index: rocm-cmake-rocm-5.0.2/share/rocm/cmake/ROCMCreatePackage.cmake
===================================================================
--- rocm-cmake-rocm-5.0.2.orig/share/rocm/cmake/ROCMCreatePackage.cmake
+++ rocm-cmake-rocm-5.0.2/share/rocm/cmake/ROCMCreatePackage.cmake
@@ -230,7 +230,6 @@ macro(rocm_create_package)
             ")
         endforeach()
     endif()
-    rocm_setup_license(${PARSE_HEADER_ONLY})
     if(PARSE_COMPONENTS)
         rocm_set_comp_cpackvar(PARSE_HEADER_ONLY "${PARSE_COMPONENTS}")
     endif()