[clang] [libc] [llvm] [AMDGPU] Use COV6 by default (PR #118515)

[Matt Arsenault via cfe-commits]

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@@ -818,6 +818,8 @@ Target Specific Changes
 AMDGPU Support
 ^^^^^^^^^^^^^^
 
+- Bump the default code object version to 6.
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arsenm wrote:

Also should update the llvm release notes 

https://github.com/llvm/llvm-project/pull/118515