Fix dxc roll

Add file to GN build that was added a couple months ago in:
https://github.com/microsoft/DirectXShaderCompiler/commit/0c9e75e7e91bb18fab101abc81d399a0296f499e
But only now fails our GN build because this change added a dep on it from DXC:
https://github.com/microsoft/DirectXShaderCompiler/commit/715dacc6654fb3d67dda3ecfa3f3891846a10405

Change-Id: Ibfedd6e115581b26466653b344dd64f49b87f72c
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/269754
Commit-Queue: Loko Kung <lokokung@google.com>
Reviewed-by: Loko Kung <lokokung@google.com>

DEPS

diff --git a/DEPS b/DEPS
index 8d34691..cd5c04b 100644
--- a/DEPS
+++ b/DEPS
@@ -344,7 +344,7 @@
   },
 
   'third_party/dxc': {
-    'url': '{chromium_git}/external/github.com/microsoft/DirectXShaderCompiler@c522461221759f1785b3434ce52ae89d6b66855a',
+    'url': '{chromium_git}/external/github.com/microsoft/DirectXShaderCompiler@c9980045a91176e5121947a43d451c76ed290b75',
   },
 
   'third_party/dxheaders': {

third_party/dxc

diff --git a/third_party/dxc b/third_party/dxc
index c522461..c998004 160000
--- a/third_party/dxc
+++ b/third_party/dxc
@@ -1 +1 @@
-Subproject commit c522461221759f1785b3434ce52ae89d6b66855a
+Subproject commit c9980045a91176e5121947a43d451c76ed290b75

third_party/gn/dxc/BUILD.gn

diff --git a/third_party/gn/dxc/BUILD.gn b/third_party/gn/dxc/BUILD.gn
index f503eeb..ccfde79 100644
--- a/third_party/gn/dxc/BUILD.gn
+++ b/third_party/gn/dxc/BUILD.gn
@@ -1240,6 +1240,7 @@
     "$dawn_dxc_dir/lib/DxcSupport/WinAdapter.cpp",
     "$dawn_dxc_dir/lib/DxcSupport/WinFunctions.cpp",
     "$dawn_dxc_dir/lib/DxcSupport/WinIncludes.cpp",
+    "$dawn_dxc_dir/lib/DxcSupport/dxcapi.extval.cpp",
     "$dawn_dxc_dir/lib/DxcSupport/dxcapi.use.cpp",
     "$dawn_dxc_dir/lib/DxcSupport/dxcmem.cpp",
     "$dawn_dxc_dir/lib/DxilContainer/DxcContainerBuilder.cpp",