[clang] [PGO] Add a clang option -fprofile-continuous that enables PGO continuous mode (PR #124353)

[Carlo Cabrera via cfe-commits]

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@@ -1886,6 +1886,11 @@ def fprofile_update_EQ : Joined<["-"], "fprofile-update=">,
     Values<"atomic,prefer-atomic,single">,
     MetaVarName<"<method>">, HelpText<"Set update method of profile counters">,
     MarshallingInfoFlag<CodeGenOpts<"AtomicProfileUpdate">>;
+def fprofile_continuous : Flag<["-"], "fprofile-continuous">,
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carlocab wrote:

Mild suggestion: `-fprofile-continuously` reads a little better. But happy with the existing flag if you feel strongly about it.

https://github.com/llvm/llvm-project/pull/124353