Teach ACLiC to build modules.

ACLiC now synthesizes a modulemap with a suffix _ACLiC_dict.modulemap. The file
contains the source file to be compiled and the corresponding library.

The modulemap is then passed to rootcling via -fmodule-map-file= flag to avoid
naming clashes with possibly existing other modulemap files.

This patch teaches cling to work with the -fmodule-map-file= flag.

ACLiC supports automatic inclusion of Rtypes.h (making ClassDef macro
available). Modules are built in isolation and are resilient to #include
of Rtypes.h at rootcling startup time. We make module Core (containing Rtypes.h)
visible via a newly implemented callback.

include/cling/Interpreter/InterpreterCallbacks.h

@@ -110,6 +110,9 @@ namespace cling {
                                    llvm::StringRef /*SearchPath*/,
                                    llvm::StringRef /*RelativePath*/,
                                    const clang::Module* /*Imported*/) {}
+    virtual void EnteredSubmodule(clang::Module* M,
+                                  clang::SourceLocation ImportLoc,
+                                  bool ForPragma) {}
 
     virtual bool FileNotFound(llvm::StringRef FileName,
                               llvm::SmallVectorImpl<char>& RecoveryPath);

lib/Interpreter/CIFactory.cpp

@@ -1236,6 +1236,13 @@ static void stringifyPreprocSetting(PreprocessorOptions& PPOpts,
                                       PP.getTargetInfo().getTriple());
     }
 
+    for (const auto& Filename : FrontendOpts.ModuleMapFiles) {
+      if (auto* File = FM.getFile(Filename))
+        PP.getHeaderSearchInfo().loadModuleMapFile(File, /*IsSystem*/ false);
+      else
+        CI->getDiagnostics().Report(diag::err_module_map_not_found) << Filename;
+    }
+
     return CI.release(); // Passes over the ownership to the caller.
   }
 

lib/Interpreter/InterpreterCallbacks.cpp

@@ -49,6 +49,12 @@ namespace cling {
                                       SearchPath, RelativePath, Imported);
     }
 
+    void EnteredSubmodule(clang::Module* M,
+                          clang::SourceLocation ImportLoc,
+                          bool ForPragma) override {
+      m_Callbacks->EnteredSubmodule(M, ImportLoc, ForPragma);
+    }
+
     virtual bool FileNotFound(llvm::StringRef FileName,
                               llvm::SmallVectorImpl<char>& RecoveryPath) {
       if (m_Callbacks)

lib/Interpreter/MultiplexInterpreterCallbacks.h

@@ -41,6 +41,12 @@ namespace cling {
                                Imported);
     }
 
+    void EnteredSubmodule(clang::Module* M, clang::SourceLocation ImportLoc,
+                          bool ForPragma) override {
+      for (auto&& cb : m_Callbacks)
+        cb->EnteredSubmodule(M, ImportLoc, ForPragma);
+    }
+
     bool FileNotFound(llvm::StringRef FileName,
                       llvm::SmallVectorImpl<char>& RecoveryPath) override {
       bool result = false;