VS: Restore support for CUDA with no optimization flags

Since commit 67de5b7b82 (VS: Suppress MSBuild default settings affected
by UseDebugLibraries, 2024-02-13, v3.30.0-rc1~538^2~1) we generate an
empty `Optimization` element for the host compiler when there are no C
or C++ optimization flags enabled.  The CUDA Toolkit Visual Studio
integration fails with an error if an empty string is inherited from the
host compiler's `Optimization` element.  If no CUDA optimization flags
are specified, write an explicit empty `Optimization` element for the
CUDA compiler too.

Fixes: #26144

Source/cmVisualStudio10TargetGenerator.cxx

@@ -3880,6 +3880,14 @@ bool cmVisualStudio10TargetGenerator::ComputeCudaOptions(
     cudaOptions.AddFlag("CudaRuntime", "None");
   }
 
+  if (this->ProjectType == VsProjectType::vcxproj && this->MSTools) {
+    // Suppress inheritance of host compiler optimization flags
+    // when the project does not specify any optimization flags for CUDA.
+    if (!cudaOptions.HasFlag("Optimization")) {
+      cudaOptions.AddFlag("Optimization", "");
+    }
+  }
+
   this->CudaOptions[configName] = std::move(pOptions);
   return true;
 }