[AIX][TOC] -mtocdata/-mno-tocdata fix non deterministic iteration order (#86840)

Failure with testcase toc-conf.c observed when building with
LLVM_REVERSE_ITERATION=ON.
Changing from using llvm::StringSet to std::set<llvm:StringRef> to
ensure iteration order is deterministic. Note: the functionality of the
feature does not require a specific iteration order, however, this will
allow testing to be consistent.
From llvm docs:
The advantages of std::set are that its iterators are stable (deleting
or inserting an element from the set does not affect iterators or
pointers to other elements) and that iteration over the set is
guaranteed to be in sorted order.

clang/lib/Driver/ToolChains/AIX.cpp

@@ -471,7 +471,7 @@ static void addTocDataOptions(const llvm::opt::ArgList &Args,
   // the global setting of tocdata in TOCDataGloballyinEffect.
   // Those that have the opposite setting to TOCDataGloballyinEffect, are added
   // to ExplicitlySpecifiedGlobals.
-  llvm::StringSet<> ExplicitlySpecifiedGlobals;
+  std::set<llvm::StringRef> ExplicitlySpecifiedGlobals;
   for (const auto Arg :
        Args.filtered(options::OPT_mtocdata_EQ, options::OPT_mno_tocdata_EQ)) {
     TOCDataSetting ArgTocDataSetting =
@@ -486,7 +486,7 @@ static void addTocDataOptions(const llvm::opt::ArgList &Args,
         ExplicitlySpecifiedGlobals.erase(Val);
   }
 
-  auto buildExceptionList = [](const llvm::StringSet<> &ExplicitValues,
+  auto buildExceptionList = [](const std::set<llvm::StringRef> &ExplicitValues,
                                const char *OptionSpelling) {
     std::string Option(OptionSpelling);
     bool IsFirst = true;
@@ -495,7 +495,7 @@ static void addTocDataOptions(const llvm::opt::ArgList &Args,
         Option += ",";
 
       IsFirst = false;
-      Option += E.first();
+      Option += E.str();
     }
     return Option;
   };

clang/test/Driver/toc-conf.c

@@ -23,7 +23,7 @@ void func() {
 
 // CHECK-CONF1-NOT: warning:
 // CHECK-CONF1: "-cc1"{{.*}}" "-mno-tocdata"
-// CHECK-CONF1: "-mtocdata=g2,g1"
+// CHECK-CONF1: "-mtocdata=g1,g2"
 
 // CHECK-CONF2-NOT: warning:
 // CHECK-CONF2: "-cc1"{{.*}}" "-mtocdata"