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

[Wael Yehia via cfe-commits]

================
@@ -3033,6 +3033,14 @@ indexed format, regardeless whether it is produced by frontend or the IR pass.
   overhead. ``prefer-atomic`` will be transformed to ``atomic`` when supported
   by the target, or ``single`` otherwise.
 
+.. option:: -fprofile-continuous
----------------
w2yehia wrote:

@david-xl is the above what you had in mind?

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