FindCUDA: Add support for generator expressions in CUDA_NVCC_FLAGS

Follow the configure_file by a file(GENERATE) so the resulting cmake
scripts used by FindCUDA for wrapping nvcc calls can now support
generator expressions in the CUDA_NVCC_FLAGS variable.

Modules/FindCUDA.cmake

@@ -1395,7 +1395,8 @@ macro(CUDA_WRAP_SRCS cuda_target format generated_files)
       set(cmake_dependency_file "${cuda_compile_intermediate_directory}/${generated_file_basename}.depend")
       set(NVCC_generated_dependency_file "${cuda_compile_intermediate_directory}/${generated_file_basename}.NVCC-depend")
       set(generated_cubin_file "${generated_file_path}/${generated_file_basename}.cubin.txt")
-      set(custom_target_script "${cuda_compile_intermediate_directory}/${generated_file_basename}.cmake")
+      set(custom_target_script_pregen "${cuda_compile_intermediate_directory}/${generated_file_basename}.cmake.pre-gen")
+      set(custom_target_script "${cuda_compile_intermediate_directory}/${generated_file_basename}$<$<BOOL:$<CONFIG>>:.$<CONFIG>>.cmake")
 
       # Setup properties for obj files:
       if( NOT cuda_compile_to_external_module )
@@ -1436,7 +1437,11 @@ macro(CUDA_WRAP_SRCS cuda_target format generated_files)
       endif()
 
       # Configure the build script
-      configure_file("${CUDA_run_nvcc}" "${custom_target_script}" @ONLY)
+      configure_file("${CUDA_run_nvcc}" "${custom_target_script_pregen}" @ONLY)
+      file(GENERATE
+        OUTPUT "${custom_target_script}"
+        INPUT "${custom_target_script_pregen}"
+        )
 
       # So if a user specifies the same cuda file as input more than once, you
       # can have bad things happen with dependencies.  Here we check an option