Introduce CDataLayout & -fvk-use-c-layout (#8136)

Closes #8112. ~~The issue asks for a "C layout", but in this PR I use
the term "CPU layout" because this naming was pre-existing in the
codebase as `kCPULayoutRulesImpl_`. The primary purpose of this layout
is to match CPU-side struct definitions with the shader side. I'm open
to better naming suggestions, though.~~

Edit: switched back to using `CDataLayout` & `-fvk-use-c-layout`, as the
CPU target depends on the object layout rules of existing CPU layout
rules, but they're incompatible with actual shaders. So a new
`kCLayoutRulesImpl_` was needed anyway.

---------

Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/source/slang/slang-ir.h b/source/slang/slang-ir.h
index 1f6418036..ad14edf21 100644
--- a/source/slang/slang-ir.h
+++ b/source/slang/slang-ir.h
@@ -524,6 +524,7 @@ enum class IRTypeLayoutRuleName
     Std430,
     Std140,
     D3DConstantBuffer,
+    C,
     _Count,
 };