Merge pull request swiftlang#32738 from varungandhi-apple/vg-fix-indirect-dep

[ModuleTrace] Track direct dependencies through #import and @_exported import

Author: varungandhi-apple

lib/ClangImporter/ClangImporter.cpp

@@ -3409,6 +3409,8 @@ void ClangModuleUnit::getImportedModules(
   if (filter.containsOnly(ModuleDecl::ImportFilterKind::ImplementationOnly))
     return;
 
+  // [Note: Pure-Clang-modules-privately-import-stdlib]:
+  // Needed for implicitly synthesized conformances.
   if (filter.contains(ModuleDecl::ImportFilterKind::Private))
     if (auto stdlib = owner.getStdlibModule())
       imports.push_back({ModuleDecl::AccessPathTy(), stdlib});