Clang: Add equal operators for ClangString

Converting them in a Utf8String in an inner loop can be quite heavy.

Change-Id: I4f2ccde47a6e3ca08ed054462eb7772ded9e55c9
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/tools/clangbackend/ipcsource/clangstring.h

@@ -85,7 +85,38 @@ public:
         return cxString.data == nullptr;
     }
 
+    friend bool operator==(const ClangString &first, const ClangString &second)
+    {
+        return std::strcmp(first.cString(), second.cString()) == 0;
+    }
 
+    template<std::size_t Size>
+    friend bool operator==(const ClangString &first, const char(&second)[Size])
+    {
+        return std::strncmp(first.cString(), second, Size) == 0; // Size includes \0
+    }
+
+    template<std::size_t Size>
+    friend bool operator==(const char(&first)[Size], const ClangString &second)
+    {
+        return second == first;
+    }
+
+    template<typename Type,
+             typename = typename std::enable_if<std::is_pointer<Type>::value>::type
+             >
+    friend bool operator==(const ClangString &first, Type second)
+    {
+        return std::strcmp(first.cString(), second) == 0;
+    }
+
+    template<typename Type,
+             typename = typename std::enable_if<std::is_pointer<Type>::value>::type
+             >
+    friend bool operator==(Type first, const ClangString &second)
+    {
+        return second == first;
+    }
 
 private:
     CXString cxString;