[clang] Add spirv-val compilation step when targeting SPIR-V (PR #188150)

[Steven Perron via cfe-commits]

================
@@ -315,6 +315,23 @@ void tools::hlsl::Validator::ConstructJob(Compilation &C, const JobAction &JA,
                                          Exec, CmdArgs, Inputs, Input));
 }
 
+void tools::hlsl::SPIRV_Validator::ConstructJob(
+    Compilation &C, const JobAction &JA, const InputInfo &Output,
+    const InputInfoList &Inputs, const ArgList &Args,
+    const char *LinkingOutput) const {
+  std::string SPIRVValPath = getToolChain().GetProgramPath("spirv-val");
+  assert(SPIRVValPath != "spirv-val" && "cannot find spirv-val");
+
+  ArgStringList CmdArgs;
+  assert(Inputs.size() == 1 && "Unable to handle multiple inputs.");
+  const InputInfo &Input = Inputs[0];
+  CmdArgs.push_back(Input.getFilename());
----------------
s-perron wrote:

You will need more arguments than this.

1. You will need to [target environment](https://github.com/KhronosGroup/SPIRV-Tools/blob/4743e69a64255650ac902d87dc51022b6604c607/tools/val/val.cpp#L80). You will have to look at the triple to get which version of spir-v you are targeting, and generate the correct command line argument.
2. We will want to use the [scalar block layout](https://github.com/KhronosGroup/SPIRV-Tools/blob/4743e69a64255650ac902d87dc51022b6604c607/tools/val/val.cpp#L61) as well. This is needed to be able to correctly represent the default HLSL memory layout.

These are the only options we set in DXC that are relevant at this time.

https://github.com/llvm/llvm-project/pull/188150