tint/test-runner: Split expectations for FXC and DXC

Change tint's `--fxc` flag to take the path of the FXC compiler DLL.
Have tint attempt to validate with both FXC and DXC if `--validate` is
passed.

Fix the 'dirsWithNoPassExpectations' logic which looks like it got
broken with the tint -> dawn merge. It also incorrectly applied
filepath.FromSlash() on windows.

Change-Id: I0f46aa5c21bc48a2abc48402c41f846aff4a8633
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/96800
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>

test/tint/buffer/storage/dynamic_index/read.wgsl.expected.fxc.hlsl

@@ -0,0 +1,42 @@
+ByteAddressBuffer s : register(t0, space0);
+
+struct tint_symbol_1 {
+  uint idx : SV_GroupIndex;
+};
+
+float2x3 tint_symbol_8(ByteAddressBuffer buffer, uint offset) {
+  return float2x3(asfloat(buffer.Load3((offset + 0u))), asfloat(buffer.Load3((offset + 16u))));
+}
+
+float3x2 tint_symbol_9(ByteAddressBuffer buffer, uint offset) {
+  return float3x2(asfloat(buffer.Load2((offset + 0u))), asfloat(buffer.Load2((offset + 8u))), asfloat(buffer.Load2((offset + 16u))));
+}
+
+typedef int4 tint_symbol_11_ret[4];
+tint_symbol_11_ret tint_symbol_11(ByteAddressBuffer buffer, uint offset) {
+  int4 arr_1[4] = (int4[4])0;
+  {
+    [loop] for(uint i_1 = 0u; (i_1 < 4u); i_1 = (i_1 + 1u)) {
+      arr_1[i_1] = asint(buffer.Load4((offset + (i_1 * 16u))));
+    }
+  }
+  return arr_1;
+}
+
+void main_inner(uint idx) {
+  const int3 a = asint(s.Load3((176u * idx)));
+  const int b = asint(s.Load(((176u * idx) + 12u)));
+  const uint3 c = s.Load3(((176u * idx) + 16u));
+  const uint d = s.Load(((176u * idx) + 28u));
+  const float3 e = asfloat(s.Load3(((176u * idx) + 32u)));
+  const float f = asfloat(s.Load(((176u * idx) + 44u)));
+  const float2x3 g = tint_symbol_8(s, ((176u * idx) + 48u));
+  const float3x2 h = tint_symbol_9(s, ((176u * idx) + 80u));
+  const int4 i[4] = tint_symbol_11(s, ((176u * idx) + 112u));
+}
+
+[numthreads(1, 1, 1)]
+void main(tint_symbol_1 tint_symbol) {
+  main_inner(tint_symbol.idx);
+  return;
+}

test/tint/buffer/storage/dynamic_index/write.wgsl.expected.fxc.hlsl

@@ -0,0 +1,44 @@
+RWByteAddressBuffer s : register(u0, space0);
+
+struct tint_symbol_1 {
+  uint idx : SV_GroupIndex;
+};
+
+void tint_symbol_8(RWByteAddressBuffer buffer, uint offset, float2x3 value) {
+  buffer.Store3((offset + 0u), asuint(value[0u]));
+  buffer.Store3((offset + 16u), asuint(value[1u]));
+}
+
+void tint_symbol_9(RWByteAddressBuffer buffer, uint offset, float3x2 value) {
+  buffer.Store2((offset + 0u), asuint(value[0u]));
+  buffer.Store2((offset + 8u), asuint(value[1u]));
+  buffer.Store2((offset + 16u), asuint(value[2u]));
+}
+
+void tint_symbol_11(RWByteAddressBuffer buffer, uint offset, int4 value[4]) {
+  int4 array[4] = value;
+  {
+    [loop] for(uint i_1 = 0u; (i_1 < 4u); i_1 = (i_1 + 1u)) {
+      buffer.Store4((offset + (i_1 * 16u)), asuint(array[i_1]));
+    }
+  }
+}
+
+void main_inner(uint idx) {
+  s.Store3((176u * idx), asuint((0).xxx));
+  s.Store(((176u * idx) + 12u), asuint(0));
+  s.Store3(((176u * idx) + 16u), asuint((0u).xxx));
+  s.Store(((176u * idx) + 28u), asuint(0u));
+  s.Store3(((176u * idx) + 32u), asuint((0.0f).xxx));
+  s.Store(((176u * idx) + 44u), asuint(0.0f));
+  tint_symbol_8(s, ((176u * idx) + 48u), float2x3((0.0f).xxx, (0.0f).xxx));
+  tint_symbol_9(s, ((176u * idx) + 80u), float3x2((0.0f).xx, (0.0f).xx, (0.0f).xx));
+  const int4 tint_symbol_13[4] = (int4[4])0;
+  tint_symbol_11(s, ((176u * idx) + 112u), tint_symbol_13);
+}
+
+[numthreads(1, 1, 1)]
+void main(tint_symbol_1 tint_symbol) {
+  main_inner(tint_symbol.idx);
+  return;
+}