[SPIR-V] Disable validation for a broken test

The code emitted with this test would not pass validation rules for
06677 as the empty cbuffers generate a UniformConstant variable with no
binding decoration.
Seems like an oversight from DXC which would be OK if it only happened with
`-fcgl` but since this also happens in `-O0` this is a bug.

Related to #7681

Author: Keenuts

tools/clang/test/CodeGenSPIRV/type.cbuffer.including.resource.hlsl

@@ -1,4 +1,5 @@
-// RUN: %dxc -T ps_6_0 -E main -fcgl  %s -spirv | FileCheck %s
+// RUN: %dxc -T ps_6_0 -E main -fcgl -Vd %s -spirv | FileCheck %s
+// FIXME(7681): Enable validation again once codegen is fixed.
 
 // CHECK-NOT: OpDecorate %buf3