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/builtins/arrayLength/deprecated.wgsl.expected.fxc.hlsl

@@ -0,0 +1,11 @@
+ByteAddressBuffer G : register(t0, space0);
+
+[numthreads(1, 1, 1)]
+void main() {
+  uint tint_symbol_1 = 0u;
+  G.GetDimensions(tint_symbol_1);
+  const uint tint_symbol_2 = ((tint_symbol_1 - 0u) / 4u);
+  const uint l1 = tint_symbol_2;
+  const uint l2 = tint_symbol_2;
+  return;
+}

test/tint/builtins/arrayLength/via_let.wgsl.expected.dxc.hlsl

@@ -0,0 +1,10 @@
+ByteAddressBuffer G : register(t0, space0);
+
+[numthreads(1, 1, 1)]
+void main() {
+  uint tint_symbol_1 = 0u;
+  G.GetDimensions(tint_symbol_1);
+  const uint tint_symbol_2 = ((tint_symbol_1 - 0u) / 4u);
+  const uint l1 = tint_symbol_2;
+  return;
+}

test/tint/builtins/arrayLength/via_let.wgsl.expected.fxc.hlsl

@@ -0,0 +1,10 @@
+ByteAddressBuffer G : register(t0, space0);
+
+[numthreads(1, 1, 1)]
+void main() {
+  uint tint_symbol_1 = 0u;
+  G.GetDimensions(tint_symbol_1);
+  const uint tint_symbol_2 = ((tint_symbol_1 - 0u) / 4u);
+  const uint l1 = tint_symbol_2;
+  return;
+}

test/tint/builtins/arrayLength/via_let_complex.wgsl.expected.dxc.hlsl

@@ -0,0 +1,10 @@
+ByteAddressBuffer G : register(t0, space0);
+
+[numthreads(1, 1, 1)]
+void main() {
+  uint tint_symbol_1 = 0u;
+  G.GetDimensions(tint_symbol_1);
+  const uint tint_symbol_2 = ((tint_symbol_1 - 0u) / 4u);
+  const uint l1 = tint_symbol_2;
+  return;
+}

test/tint/builtins/arrayLength/via_let_complex.wgsl.expected.fxc.hlsl

@@ -0,0 +1,10 @@
+ByteAddressBuffer G : register(t0, space0);
+
+[numthreads(1, 1, 1)]
+void main() {
+  uint tint_symbol_1 = 0u;
+  G.GetDimensions(tint_symbol_1);
+  const uint tint_symbol_2 = ((tint_symbol_1 - 0u) / 4u);
+  const uint l1 = tint_symbol_2;
+  return;
+}

test/tint/builtins/arrayLength/via_let_complex_no_struct.wgsl.expected.dxc.hlsl

@@ -0,0 +1,10 @@
+ByteAddressBuffer G : register(t0, space0);
+
+[numthreads(1, 1, 1)]
+void main() {
+  uint tint_symbol_1 = 0u;
+  G.GetDimensions(tint_symbol_1);
+  const uint tint_symbol_2 = (tint_symbol_1 / 4u);
+  const uint l1 = tint_symbol_2;
+  return;
+}

test/tint/builtins/arrayLength/via_let_complex_no_struct.wgsl.expected.fxc.hlsl

@@ -0,0 +1,10 @@
+ByteAddressBuffer G : register(t0, space0);
+
+[numthreads(1, 1, 1)]
+void main() {
+  uint tint_symbol_1 = 0u;
+  G.GetDimensions(tint_symbol_1);
+  const uint tint_symbol_2 = (tint_symbol_1 / 4u);
+  const uint l1 = tint_symbol_2;
+  return;
+}

test/tint/builtins/arrayLength/via_let_no_struct.wgsl.expected.dxc.hlsl

@@ -0,0 +1,10 @@
+ByteAddressBuffer G : register(t0, space0);
+
+[numthreads(1, 1, 1)]
+void main() {
+  uint tint_symbol_1 = 0u;
+  G.GetDimensions(tint_symbol_1);
+  const uint tint_symbol_2 = (tint_symbol_1 / 4u);
+  const uint l1 = tint_symbol_2;
+  return;
+}

test/tint/builtins/arrayLength/via_let_no_struct.wgsl.expected.fxc.hlsl

@@ -0,0 +1,10 @@
+ByteAddressBuffer G : register(t0, space0);
+
+[numthreads(1, 1, 1)]
+void main() {
+  uint tint_symbol_1 = 0u;
+  G.GetDimensions(tint_symbol_1);
+  const uint tint_symbol_2 = (tint_symbol_1 / 4u);
+  const uint l1 = tint_symbol_2;
+  return;
+}