[clang][ssaf] Return StringRef from toString(BuildNamespaceKind)

Author: jkorous-apple

clang/include/clang/Analysis/Scalable/Model/BuildNamespace.h

@@ -21,7 +21,7 @@ enum class BuildNamespaceKind : unsigned short {
   LinkUnit
 };
 
-std::string toString(BuildNamespaceKind BNK);
+llvm::StringRef toString(BuildNamespaceKind BNK);
 
 std::optional<BuildNamespaceKind> parseBuildNamespaceKind(llvm::StringRef Str);
 

clang/lib/Analysis/Scalable/Model/BuildNamespace.cpp

@@ -11,7 +11,7 @@
 
 namespace clang::ssaf {
 
-std::string toString(BuildNamespaceKind BNK) {
+llvm::StringRef toString(BuildNamespaceKind BNK) {
   switch(BNK) {
     case BuildNamespaceKind::CompilationUnit: return "compilation_unit";
     case BuildNamespaceKind::LinkUnit: return "link_unit";