Clang: Compile fix for older clang

This patch is needed due to some issues of an older STL
implementation. The patch can safely be reverted when
Xcode 8 is marked as outdated.

Change-Id: I0f66eb6f3a0ae71f0da3f5678d9b4d47cdf146bf
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/libs/clangsupport/generatedfiles.cpp

@@ -26,8 +26,8 @@
 #include "generatedfiles.h"
 
 namespace ClangBackEnd {
-template<class Type>
-void GeneratedFiles::updateInternal(Type &&fileContainers)
+
+void GeneratedFiles::update(V2::FileContainers &&fileContainers)
 {
     V2::FileContainers unionFileContainers;
     unionFileContainers.reserve(m_fileContainers.size() + fileContainers.size());
@@ -46,14 +46,23 @@ void GeneratedFiles::updateInternal(Type &&fileContainers)
     m_fileContainers = std::move(unionFileContainers);
 }
 
-void GeneratedFiles::update(V2::FileContainers &&fileContainers)
-{
-    updateInternal(std::move(fileContainers));
-}
-
 void GeneratedFiles::update(const V2::FileContainers &fileContainers)
 {
-    updateInternal(fileContainers);
+    V2::FileContainers unionFileContainers;
+    unionFileContainers.reserve(m_fileContainers.size() + fileContainers.size());
+
+    auto compare = [] (const V2::FileContainer &first, const V2::FileContainer &second) {
+        return first.filePath < second.filePath;
+    };
+
+    std::set_union(fileContainers.begin(),
+                   fileContainers.end(),
+                   std::make_move_iterator(m_fileContainers.begin()),
+                   std::make_move_iterator(m_fileContainers.end()),
+                   std::back_inserter(unionFileContainers),
+                   compare);
+
+    m_fileContainers = std::move(unionFileContainers);
 }
 
 class Compare {

src/libs/clangsupport/generatedfiles.h

@@ -37,9 +37,6 @@ public:
     void remove(const FilePaths &filePaths);
 
     const V2::FileContainers &fileContainers() const;
-private:
-    template<class Type>
-    void updateInternal(Type &&fileContainers);
 
 private:
     V2::FileContainers m_fileContainers;