[HLSL] Add option for VK layouts

We add the options to the driver, so that the one option that is being
implemented at this time can be used. Issue an error for the other
options.

When we start to implement the other options, we will have to figure out
how to pass which  option is active to clang.

Author: s-perron

clang/include/clang/Driver/Options.td

@@ -9323,13 +9323,13 @@ def fspv_extension_EQ
 def fvk_use_dx_layout
     : DXCFlag<"fvk-use-dx-layout">,
       HelpText<"Use DirectX memory layout for Vulkan resources.">;
-def fvk_use_gl_layout
-    : DXCFlag<"fvk-use-gl-layout">,
-      HelpText<"Use strict OpenGL std140/std430 memory layout for Vulkan resources.">;
+def fvk_use_gl_layout : DXCFlag<"fvk-use-gl-layout">,
+                        HelpText<"Use strict OpenGL std140/std430 memory "
+                                 "layout for Vulkan resources.">;
 def fvk_use_scalar_layout
     : DXCFlag<"fvk-use-scalar-layout">,
       HelpText<"Use scalar memory layout for Vulkan resources.">;
-      
+
 def no_wasm_opt : Flag<["--"], "no-wasm-opt">,
   Group<m_Group>,
   HelpText<"Disable the wasm-opt optimizer">,

clang/test/Driver/HLSL/dxc_fvk_layout.hlsl

@@ -0,0 +1,8 @@
+// No errors. Otherwise nothing observable.
+// RUN: %clang_dxc -fvk-use-dx-layout -spirv -Tlib_6_7 -### %s
+
+// RUN: not %clang_dxc -fvk-use-scalar-layout -spirv -Tlib_6_7 -### %s 2>&1 | FileCheck %s -check-prefix=SCALAR
+// SCALAR: error: the clang compiler does not support '-fvk-use-scalar-layout'
+
+// RUN: not %clang_dxc -fvk-use-gl-layout -spirv -Tlib_6_7 -### %s 2>&1 | FileCheck %s -check-prefix=GL
+// GL: error: the clang compiler does not support '-fvk-use-gl-layout'