CUDA: Do not device link if target has no CUDA usage

When CUDA is enabled, and a pure non-CUDA target has
CMAKE_CUDA_SEPARABLE_COMPILATION enabled, don't actually perform
the device linking step, as it will fail. A target that has
CMAKE_CUDA_SEPARABLE_COMPILATION enabled must also have CUDA
usage (either itself, or something it links to).

Fixes: #20182

3 files changed, 9 insertions, 0 deletions

diff --git a/Tests/Cuda/CMakeLists.txt b/Tests/Cuda/CMakeLists.txt
index a30071f..44c6005 100644
--- a/Tests/Cuda/CMakeLists.txt
+++ b/Tests/Cuda/CMakeLists.txt
@@ -4,6 +4,7 @@ ADD_TEST_MACRO(Cuda.ConsumeCompileFeatures CudaConsumeCompileFeatures)
 ADD_TEST_MACRO(Cuda.ObjectLibrary CudaObjectLibrary)
 ADD_TEST_MACRO(Cuda.MixedStandardLevels MixedStandardLevels)
 ADD_TEST_MACRO(Cuda.NotEnabled CudaNotEnabled)
+ADD_TEST_MACRO(Cuda.SeparableCompCXXOnly SeparableCompCXXOnly)
 ADD_TEST_MACRO(Cuda.ToolkitInclude CudaToolkitInclude)
 ADD_TEST_MACRO(Cuda.ProperDeviceLibraries ProperDeviceLibraries)
 ADD_TEST_MACRO(Cuda.ProperLinkFlags ProperLinkFlags)
diff --git a/Tests/Cuda/SeparableCompCXXOnly/CMakeLists.txt b/Tests/Cuda/SeparableCompCXXOnly/CMakeLists.txt
new file mode 100644
index 0000000..97670e3
--- /dev/null
+++ b/Tests/Cuda/SeparableCompCXXOnly/CMakeLists.txt
@@ -0,0 +1,3 @@
+project(SeparableCompCXXOnly LANGUAGES CXX CUDA)
+set(CMAKE_CUDA_SEPARABLE_COMPILATION ON)
+add_executable(SeparableCompCXXOnly main.cpp)
diff --git a/Tests/Cuda/SeparableCompCXXOnly/main.cpp b/Tests/Cuda/SeparableCompCXXOnly/main.cpp
new file mode 100644
index 0000000..8135246
--- /dev/null
+++ b/Tests/Cuda/SeparableCompCXXOnly/main.cpp
@@ -0,0 +1,5 @@
+
+int main(int, char const* [])
+{
+  return 0;
+}