Allow use of dxc compiler for DXIL generation (#241)

- Add shader model 6.0, 6.1, and 6.2 targets

- Add DXIL and DXIL assembly as output formats

- Add header for DXC API to `external/`

- Add `dxc-support.cpp` that wraps usage of the API

- Add `-pass-through dxc` option, equivalent to what we have for `fxc`

Notes:
* This does *not* include any logic to add `dxcompiler.dll` to our build process; that is way out of scope for the build complexity I'm ready to deal with
* For right now, the use of `dxcompiler.dll` is hard-coded, and it must be discoverable in the current executable's search path; options to customize can come later
* The `-pass-through` option is kind of silly because the code doesn't actually pay attention to the value (just whether it is set). If you set it to `fxc` but ask for DXIL, we pass through `dxc` anyway.

1 files changed, 2 insertions, 0 deletions

diff --git a/source/slang/type-layout.cpp b/source/slang/type-layout.cpp
index 19b9a435e..0825da6b4 100644
--- a/source/slang/type-layout.cpp
+++ b/source/slang/type-layout.cpp
@@ -621,6 +621,8 @@ LayoutRulesFamilyImpl* GetLayoutRulesFamilyImpl(CodeGenTarget target)
     case CodeGenTarget::HLSL:
     case CodeGenTarget::DXBytecode:
     case CodeGenTarget::DXBytecodeAssembly:
+    case CodeGenTarget::DXIL:
+    case CodeGenTarget::DXILAssembly:
         return &kHLSLLayoutRulesFamilyImpl;
 
     case CodeGenTarget::GLSL: