Remove -l flag from Swift interim driver.

Being able to pass -l to the driver isn't so interesting, and it's an
extra field that lives on TranslationUnit for no reason. Just remove it.

This doesn't interfere with autolinking, i.e. inferring -l flags based on
imported modules.

Swift SVN r9241

include/swift/AST/Module.h

@@ -458,9 +458,6 @@ public:
 /// \sa SourceFile
 class TranslationUnit : public Module {
 private:
-  /// The list of libraries specified as link-time dependencies at compile time.
-  ArrayRef<LinkLibrary> LinkLibraries;
-
   /// If non-NULL, an plug-in that should be used when performing external
   /// lookups.
   ExternalNameLookup *ExternalLookup = nullptr;
@@ -473,14 +470,6 @@ public:
     : Module(ModuleKind::TranslationUnit, Name, C) {
   }
   
-  void setLinkLibraries(ArrayRef<LinkLibrary> libs) {
-    assert(LinkLibraries.empty() && "link libraries already set");
-    LinkLibraries = libs;
-  }
-  ArrayRef<LinkLibrary> getLinkLibraries() const {
-    return LinkLibraries;
-  }
-
   void clearLookupCache();
 
   void cacheVisibleDecls(SmallVectorImpl<ValueDecl *> &&globals) const;

include/swift/Frontend/Frontend.h

@@ -47,7 +47,6 @@ class CompilerInvocation {
   std::string ClangModuleCachePath;
   std::vector<std::string> ImportSearchPaths;
   std::vector<std::string> FrameworkSearchPaths;
-  SmallVector<LinkLibrary, 4> LinkLibraries;
   std::string RuntimeIncludePath;
   std::string SDKPath;
   std::vector<std::string> ExtraClangArgs;
@@ -121,14 +120,6 @@ public:
     return ExtraClangArgs;
   }
 
-  void addLinkLibrary(StringRef name, LibraryKind kind) {
-    LinkLibraries.push_back({name, kind});
-  }
-
-  ArrayRef<LinkLibrary> getLinkLibraries() const {
-    return LinkLibraries;
-  }
-
   void setMainExecutablePath(StringRef Path);
 
   void setRuntimeIncludePath(StringRef Path) {

lib/AST/Module.cpp

@@ -1038,20 +1038,12 @@ void Module::forAllVisibleModules(Optional<AccessPathTy> thisPath,
 void Module::collectLinkLibraries(LinkLibraryCallback callback) {
   forAllImportedModules<false>(this, AccessPathTy(),
                                [=](ImportedModule import) -> bool {
-    Module *module = import.second;
-    if (isa<BuiltinModule>(module)) {
-      // The Builtin module requires no libraries.
+    auto loadedModule = dyn_cast<LoadedModule>(import.second);
+    if (!loadedModule)
       return true;
-    }
-    
-    if (auto TU = dyn_cast<TranslationUnit>(module)) {
-      for (auto lib : TU->getLinkLibraries())
-        callback(lib);
-      return true;
-    }
-    
-    ModuleLoader &owner = cast<LoadedModule>(module)->getOwner();
-    owner.getLinkLibraries(module, callback);
+
+    ModuleLoader &owner = loadedModule->getOwner();
+    owner.getLinkLibraries(loadedModule, callback);
     return true;
   });
 }

lib/Frontend/CompilerInvocation.cpp

@@ -124,10 +124,6 @@ bool CompilerInvocation::parseArgs(ArrayRef<const char *> Args,
       LangOpts.DebugConstraintSolver = true;
       break;
 
-    case OPT_link_library:
-      addLinkLibrary(InputArg->getValue(), LibraryKind::Library);
-      break;
-      
     case OPT_std_EQ:
       if (strcmp(InputArg->getValue(), "axle") == 0)
         LangOpts.Axle = true;

lib/Frontend/Frontend.cpp

@@ -123,8 +123,6 @@ void swift::CompilerInstance::doIt() {
   TU = new (*Context) TranslationUnit(ID, *Context);
   Context->LoadedModules[ID.str()] = TU;
 
-  TU->setLinkLibraries(Invocation.getLinkLibraries());
-
   auto *SingleInputFile =
     new (*Context) SourceFile(*TU, Kind, Invocation.getParseStdlib());
   TU->MainSourceFile = SingleInputFile;

lib/Frontend/FrontendOptions.td

@@ -20,9 +20,6 @@ def parse_as_library : Flag<["-"], "parse-as-library">,
 def parse_stdlib : Flag<["-"], "parse-stdlib">,
   HelpText<"Parse the input as the swift standard library">;
 
-def link_library : Joined<["-"], "l">,
-  HelpText<"Link the given library into the output product">;
-
 def Xclang : Separate<["-"], "Xclang">,
   HelpText<"Pass <arg> to the clang importer">;