CUDA: Fix tests with CUDAARCHS set

With CUDAARCHS there's the possibility of tests being run with multiple
architectures or having CMAKE_CUDA_ARCHITECTURES set with NVCC despite CMP0104
being OLD.
Fix a few tests to work properly in such cases.

Tests/CudaOnly/CompileFlags/CMakeLists.txt

@@ -8,6 +8,7 @@ if(CMAKE_CUDA_COMPILER_ID STREQUAL "NVIDIA")
   target_compile_options(CudaOnlyCompileFlags PRIVATE
     -gencode arch=compute_50,code=compute_50
   )
+  set_property(TARGET CudaOnlyCompileFlags PROPERTY CUDA_ARCHITECTURES)
 else()
   set_property(TARGET CudaOnlyCompileFlags PROPERTY CUDA_ARCHITECTURES 50-real)
 endif()

Tests/CudaOnly/ExportPTX/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.8)
+cmake_minimum_required(VERSION 3.19)
 project (ExportPTX CUDA)
 
 #Goal for this example:
@@ -6,6 +6,10 @@ project (ExportPTX CUDA)
 # How to reference PTX files for custom commands
 # How to install PTX files
 
+# PTX can be compiled only for a single virtual architecture at a time
+list(SUBLIST CMAKE_CUDA_ARCHITECTURES 0 1 CMAKE_CUDA_ARCHITECTURES)
+string(APPEND CMAKE_CUDA_ARCHITECTURES "-virtual")
+
 add_library(CudaPTX OBJECT kernelA.cu kernelB.cu)
 set_property(TARGET CudaPTX PROPERTY CUDA_PTX_COMPILATION ON)
 

Tests/RunCMake/CMP0104/CMP0104-OLD.cmake

@@ -1,3 +1,5 @@
+set(ENV{CUDAARCHS})
+
 cmake_policy(SET CMP0104 OLD)
 include(CMP0104-Common.cmake)