GLSL/HLSL: Disallow VariablePointers capability outright.

Cannot be supported, error out early.

shaders-hlsl-no-opt/asm/comp/storage-buffer-basic.nofxc.asm.comp

@@ -4,9 +4,9 @@
 ; Bound: 31
 ; Schema: 0
                OpCapability Shader
-               OpCapability VariablePointers
+               ;OpCapability VariablePointers
                OpExtension "SPV_KHR_storage_buffer_storage_class"
-               OpExtension "SPV_KHR_variable_pointers"
+               ;OpExtension "SPV_KHR_variable_pointers"
                OpMemoryModel Logical GLSL450
                OpEntryPoint GLCompute %22 "main" %gl_WorkGroupID
                OpSource OpenCL_C 120

shaders-no-opt/asm/comp/storage-buffer-basic.asm.comp

@@ -4,9 +4,9 @@
 ; Bound: 31
 ; Schema: 0
                OpCapability Shader
-               OpCapability VariablePointers
+               ;OpCapability VariablePointers
                OpExtension "SPV_KHR_storage_buffer_storage_class"
-               OpExtension "SPV_KHR_variable_pointers"
+               ;OpExtension "SPV_KHR_variable_pointers"
                OpMemoryModel Logical GLSL450
                OpEntryPoint GLCompute %22 "main" %gl_WorkGroupID
                OpSource OpenCL_C 120

spirv_glsl.cpp

@@ -502,6 +502,10 @@ void CompilerGLSL::find_static_extensions()
 			}
 			break;
 
+		case CapabilityVariablePointers:
+		case CapabilityVariablePointersStorageBuffer:
+			SPIRV_CROSS_THROW("VariablePointers capability is not supported in GLSL.");
+
 		default:
 			break;
 		}

spirv_hlsl.cpp

@@ -5616,6 +5616,12 @@ void CompilerHLSL::validate_shader_model()
 			if (hlsl_options.shader_model < 51)
 				SPIRV_CROSS_THROW(
 				    "Shader model 5.1 or higher is required to use bindless resources or NonUniformResourceIndex.");
+			break;
+
+		case CapabilityVariablePointers:
+		case CapabilityVariablePointersStorageBuffer:
+			SPIRV_CROSS_THROW("VariablePointers capability is not supported in HLSL.");
+
 		default:
 			break;
 		}