[Sema] Only look for PrivateFrameworks on Darwin

Author: xymus

Diff for: lib/AST/Module.cpp

@@ -2259,6 +2259,8 @@ ModuleLibraryLevelRequest::evaluate(Evaluator &evaluator,
 
   /// Is \p modulePath from System/Library/PrivateFrameworks/?
   auto fromPrivateFrameworks = [&](StringRef modulePath) -> bool {
+    if (!ctx.LangOpts.Target.isOSDarwin()) return false;
+
     namespace path = llvm::sys::path;
     SmallString<128> scratch;
     scratch = ctx.SearchPathOpts.SDKPath;

Diff for: test/Sema/implementation-only-import-suggestion.swift

@@ -1,4 +1,5 @@
 // RUN: %empty-directory(%t)
+// REQUIRES: VENDOR=apple
 
 /// Expect warnings when building a public client.
 // RUN: %target-swift-frontend -sdk %S/Inputs/public-private-sdk -typecheck -module-cache-path %t %s \