Merge pull request #1617 from ericniebler/default-cmake-cuda-architectures-to-native

if `CMAKE_CUDA_ARCHITECTURES` is not set, set it to `"native"`

Author: ericniebler

CMakeLists.txt

@@ -311,6 +311,10 @@ if(STDEXEC_ENABLE_CUDA)
     target_compile_features(nvexec INTERFACE cuda_std_20)
     target_link_libraries(nvexec INTERFACE STDEXEC::stdexec)
 
+    if(NOT CMAKE_CUDA_ARCHITECTURES)
+      set(CMAKE_CUDA_ARCHITECTURES "native")
+    endif()
+
     set(_gpus)
     foreach(_arch IN LISTS CMAKE_CUDA_ARCHITECTURES)
       if(_arch MATCHES "-real")
@@ -321,6 +325,8 @@ if(STDEXEC_ENABLE_CUDA)
         string(PREPEND _arch "cc")
       elseif(_arch MATCHES "^[0-9]+$")
         string(PREPEND _arch "cc")
+      elseif(_arch MATCHES "^native$")
+        string(PREPEND _arch "cc")
       endif()
       list(APPEND _gpus "${_arch}")
     endforeach()