[clang] [Feature]: merge host and kernel dependencies for heterogeneous compilation (PR #119513)

[Yaxun Liu via cfe-commits]

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@@ -798,6 +798,8 @@ def MD : Flag<["-"], "MD">, Group<M_Group>,
     HelpText<"Write a depfile containing user and system headers">;
 def MMD : Flag<["-"], "MMD">, Group<M_Group>,
     HelpText<"Write a depfile containing user headers">;
+def MMMD : Flag<["-"], "MMMD">, Group<M_Group>,
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yxsamliu wrote:

I am wondering whether we could keep using the old compiler option `-MMD` for this new behavior, and use triple/language etc to choose the new behavior. The reason is that users usually use the existing options in their cmake file for dependency files. 

https://github.com/llvm/llvm-project/pull/119513