Roll DirectX Shader Compiler from 438781364eea to fadd62719918 (3 revisions)

https://chromium.googlesource.com/external/github.com/microsoft/DirectXShaderCompiler.git/+log/438781364eea..fadd62719918

2024-01-30 brioche@google.com [SPIR-V] Fix invalid optional read (#6221)
2024-01-30 stevenperron@google.com [SPIRV] Reimplement flat conversion. (#6189)
2024-01-30 sudonatalie@google.com [SPIR-V] Update SPV_GOOGLE_user_type (#6217)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/directx-shader-compiler-dawn
Please CC alanbaker@google.com,webgpu-developers@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in DirectX Shader Compiler: https://github.com/microsoft/DirectXShaderCompiler/issues/new/choose
To file a bug in Dawn: https://bugs.chromium.org/p/dawn/issues/entry

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

Bug: None
Tbr: alanbaker@google.com
Change-Id: If876fb1725f2219a95ab3488d40ffb5d14ab3883
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/172341
Bot-Commit: Dawn Autoroller <dawn-autoroll@skia-public.iam.gserviceaccount.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Dawn Autoroller <dawn-autoroll@skia-public.iam.gserviceaccount.com>
Reviewed-by: Alan Baker <alanbaker@google.com>
diff --git a/DEPS b/DEPS
index e086676..8e33264 100644
--- a/DEPS
+++ b/DEPS
@@ -197,7 +197,7 @@
   },
 
   'third_party/dxc': {
-    'url': '{chromium_git}/external/github.com/microsoft/DirectXShaderCompiler@438781364eea22d188b337be1dfa4174ed7d928c',
+    'url': '{chromium_git}/external/github.com/microsoft/DirectXShaderCompiler@fadd62719918f6313e599c9d9d646591e59f6cde',
   },
 
   'third_party/dxheaders': {
diff --git a/third_party/dxc b/third_party/dxc
index 4387813..fadd627 160000
--- a/third_party/dxc
+++ b/third_party/dxc
@@ -1 +1 @@
-Subproject commit 438781364eea22d188b337be1dfa4174ed7d928c
+Subproject commit fadd62719918f6313e599c9d9d646591e59f6cde