[llvm] Add !metadata_section_kind global variable metadata (PR #211524)

[Orlando Cazalet-Hyams via llvm-commits]

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@@ -7789,6 +7789,26 @@ sections that the user does not want removed after linking.
 !0 = !{}
 ```
 
+#### '`metadata_section_kind`' Metadata
+
+`metadata_section_kind` metadata may be attached to a global variable to signify
+that its section should be treated as "metadata" by LLVM, meaning the the
+section will be generic by default without any flags, unless the section has a
+special name (e.g., `"llvm.metadata"`). Incompatible with `!exclude`; in
+practice, one may be ignored by LLVM. This option is only valid for global
+variables with an explicit section targeting ELF or COFF.
+
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OCHyams wrote:

seems reasonable, done :)

https://github.com/llvm/llvm-project/pull/211524