[SourceKit] Make sure to propagate the SIL options from the compiler invocation when doing performSILGeneration() to get the SIL diagnostics

rdar://32329669

tools/SourceKit/lib/SwiftLang/SwiftASTManager.cpp

@@ -835,7 +835,7 @@ ASTUnitRef ASTProducer::createASTUnit(SwiftASTManager::Implementation &MgrImpl,
     // don't block any other AST processing for the same SwiftInvocation.
 
     if (auto SF = CompIns.getPrimarySourceFile()) {
-      SILOptions SILOpts;
+      SILOptions SILOpts = Invocation.getSILOptions();
       std::unique_ptr<SILModule> SILMod = performSILGeneration(*SF, SILOpts);
       runSILDiagnosticPasses(*SILMod);
     }