Suppress MultisampledSamplingTest if the toggle use_dxc is enabled on D3D12

The suppression must be added before creating shader module in SetUp()
because the test fails with shader compiler error.

Bug: tint:1976
Change-Id: If29dedbb83b43d07c854754a93a4c2cd6d6659ab
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/140640
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Hao Li <hao.x.li@intel.com>

src/dawn/tests/end2end/MultisampledSamplingTests.cpp

diff --git a/src/dawn/tests/end2end/MultisampledSamplingTests.cpp b/src/dawn/tests/end2end/MultisampledSamplingTests.cpp
index c08ecc0..ac82523 100644
--- a/src/dawn/tests/end2end/MultisampledSamplingTests.cpp
+++ b/src/dawn/tests/end2end/MultisampledSamplingTests.cpp
@@ -51,6 +51,10 @@
     void SetUp() override {
         DawnTest::SetUp();
 
+        // TODO(crbug.com/tint/1976): DXC fails to compile the following compute shader because the
+        // coordinate in texture load is not interpreted as an integer vector.
+        DAWN_SUPPRESS_TEST_IF(IsD3D12() && HasToggleEnabled("use_dxc"));
+
         {
             utils::ComboRenderPipelineDescriptor desc;