[llvm] [vim] set commentstring (PR #71838)

[Fangrui Song via llvm-commits]

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@@ -270,3 +270,5 @@ if version >= 508 || !exists("did_c_syn_inits")
 endif
 
 let b:current_syntax = "llvm"
+
+setlocal commentstring=;\ %s
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MaskRay wrote:

Add this below `syn match llvmSpecialComment /`? Not many syntax files in `/usr/share/vim/vim90/syntax` set `commentstring`. When then do, they place `commentstring` near `syntax ...Comment`

https://github.com/llvm/llvm-project/pull/71838