[Clang][NFC] Use correct tool name for NVIDIA's 'nvlink'

Summary:
This step was incorrectly called 'fatbinary', so if it failed here it
would say 'fatbinary' was the cause of the failure. This is actually
'nvlink' so we should adjust this.

clang/lib/Driver/ToolChains/Cuda.h

@@ -110,7 +110,7 @@ class LLVM_LIBRARY_VISIBILITY FatBinary : public Tool {
 // Runs nvlink, which links GPU object files ("cubin" files) into a single file.
 class LLVM_LIBRARY_VISIBILITY Linker : public Tool {
 public:
-  Linker(const ToolChain &TC) : Tool("NVPTX::Linker", "fatbinary", TC) {}
+  Linker(const ToolChain &TC) : Tool("NVPTX::Linker", "nvlink", TC) {}
 
   bool hasIntegratedCPP() const override { return false; }