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

[Fangrui Song via cfe-commits]

================
@@ -133,6 +133,16 @@ std::string getDefaultProfileGenName() {
              : "default_%m.profraw";
 }
 
+// Path and name of file used for profile generation
+std::string getProfileGenName(const CodeGenOptions &CodeGenOpts) {
----------------
MaskRay wrote:

Move outside of the anonymous namespace and use `static` https://llvm.org/docs/CodingStandards.html#use-namespace-qualifiers-to-implement-previously-declared-functions

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