Fix overrides in array size.

This CL fixes the usage of overrides in array sizes. Currently
the usage will generate a validation error as we check that the
array size is const.

Bug: tint:1660
Change-Id: Ibf440905c30a73b581d55b0c071b8621b61605e6
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/101900
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: dan sinclair <dsinclair@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>

test/tint/bug/tint/1660.wgsl

@@ -0,0 +1,5 @@
+// flags: --transform substitute_override
+
+override size = 2;
+
+var<workgroup> a : array<f32, size>;

test/tint/bug/tint/1660.wgsl.expected.dxc.hlsl

@@ -0,0 +1,6 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+groupshared float a[2];

test/tint/bug/tint/1660.wgsl.expected.fxc.hlsl

@@ -0,0 +1,6 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+groupshared float a[2];

test/tint/bug/tint/1660.wgsl.expected.glsl

@@ -0,0 +1,7 @@
+#version 310 es
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void unused_entry_point() {
+  return;
+}
+shared float a[2];

test/tint/bug/tint/1660.wgsl.expected.msl

@@ -0,0 +1,3 @@
+#include <metal_stdlib>
+
+using namespace metal;

test/tint/bug/tint/1660.wgsl.expected.spvasm

@@ -0,0 +1,24 @@
+; SPIR-V
+; Version: 1.3
+; Generator: Google Tint Compiler; 0
+; Bound: 11
+; Schema: 0
+               OpCapability Shader
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint GLCompute %unused_entry_point "unused_entry_point"
+               OpExecutionMode %unused_entry_point LocalSize 1 1 1
+               OpName %a "a"
+               OpName %unused_entry_point "unused_entry_point"
+               OpDecorate %_arr_float_uint_2 ArrayStride 4
+      %float = OpTypeFloat 32
+       %uint = OpTypeInt 32 0
+     %uint_2 = OpConstant %uint 2
+%_arr_float_uint_2 = OpTypeArray %float %uint_2
+%_ptr_Workgroup__arr_float_uint_2 = OpTypePointer Workgroup %_arr_float_uint_2
+          %a = OpVariable %_ptr_Workgroup__arr_float_uint_2 Workgroup
+       %void = OpTypeVoid
+          %7 = OpTypeFunction %void
+%unused_entry_point = OpFunction %void None %7
+         %10 = OpLabel
+               OpReturn
+               OpFunctionEnd

test/tint/bug/tint/1660.wgsl.expected.wgsl

@@ -0,0 +1,3 @@
+const size = 2;
+
+var<workgroup> a : array<f32, size>;