[clang] Fix sorting module headers (#73146)

Struct Module::Header is not a POD type. As such, qsort() and
llvm::array_pod_sort() must not be used to sort it. This became an issue
with the new implementation of qsort() in glibc 2.39 that is not
guaranteed to be a stable sort, causing Headers to be re-ordered and
corrupted.

Replace the usage of llvm::array_pod_sort() with std::stable_sort() in
order to fix this issue. The signature of compareModuleHeaders() has to
be modified.

Fixes #73145.

(cherry picked from commit cf1bde3)

Author: tuliom

clang/lib/Lex/ModuleMap.cpp

@@ -2481,9 +2481,9 @@ void ModuleMapParser::parseHeaderDecl(MMToken::TokenKind LeadingToken,
       << FixItHint::CreateReplacement(CurrModuleDeclLoc, "framework module");
 }
 
-static int compareModuleHeaders(const Module::Header *A,
-                                const Module::Header *B) {
-  return A->NameAsWritten.compare(B->NameAsWritten);
+static bool compareModuleHeaders(const Module::Header &A,
+                                 const Module::Header &B) {
+  return A.NameAsWritten < B.NameAsWritten;
 }
 
 /// Parse an umbrella directory declaration.
@@ -2546,7 +2546,7 @@ void ModuleMapParser::parseUmbrellaDirDecl(SourceLocation UmbrellaLoc) {
     }
 
     // Sort header paths so that the pcm doesn't depend on iteration order.
-    llvm::array_pod_sort(Headers.begin(), Headers.end(), compareModuleHeaders);
+    std::stable_sort(Headers.begin(), Headers.end(), compareModuleHeaders);
 
     for (auto &Header : Headers)
       Map.addHeader(ActiveModule, std::move(Header), ModuleMap::TextualHeader);