[Swiftify] Always skip safe wrappers when building the stdlib

_SwiftifyImport assumes types like Swift.Int, Swift.UnsafePointer<T> and
Swift.Span<T> are available. This is not the case when building the
stdlib itself. Disable safe interop in the stdlib to prevent errors.
This currently has no effect, but will when this feature is enabled by
default, which I have manually tested.

Author: hnrklssn

include/swift/Basic/LangOptions.h

@@ -1148,6 +1148,10 @@ namespace swift {
     /// ones to apply.
     bool LoadVersionIndependentAPINotes = false;
 
+    /// Whether the importer should skip SafeInteropWrappers, even though the
+    /// feature is enabled.
+    bool DisableSafeInteropWrappers = false;
+
     /// Return a hash code of any components from these options that should
     /// contribute to a Swift Bridging PCH hash.
     llvm::hash_code getPCHHashComponents() const {

lib/ClangImporter/ImportDecl.cpp

@@ -9484,7 +9484,8 @@ static StringRef getAttributeName(const clang::CountAttributedType *CAT) {
 }
 
 void ClangImporter::Implementation::swiftify(AbstractFunctionDecl *MappedDecl) {
-  if (!SwiftContext.LangOpts.hasFeature(Feature::SafeInteropWrappers))
+  if (!SwiftContext.LangOpts.hasFeature(Feature::SafeInteropWrappers) ||
+      SwiftContext.ClangImporterOpts.DisableSafeInteropWrappers)
     return;
   auto ClangDecl =
       dyn_cast_or_null<clang::FunctionDecl>(MappedDecl->getClangDecl());

lib/Frontend/CompilerInvocation.cpp

@@ -2175,6 +2175,8 @@ static bool ParseClangImporterArgs(ClangImporterOptions &Opts, ArgList &Args,
 
   Opts.LoadVersionIndependentAPINotes |= Args.hasArg(OPT_version_independent_apinotes);
 
+  Opts.DisableSafeInteropWrappers |= FrontendOpts.ParseStdlib;
+
   if (FrontendOpts.DisableImplicitModules)
     Opts.DisableImplicitClangModules = true;