CMakeProject: Prefer assignment to out parameter

Also change method names from update...() to create...() and mark as
const. This communicates that the objects the methods are called on are
neither altered nor updated.

Change-Id: I29e84dc398ded3ffcbf90741227362c6b4be2bf9
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/cmakeprojectmanager/servermodereader.cpp

@@ -356,8 +356,10 @@ void ServerModeReader::generateProjectTree(CMakeProjectNode *root,
                        std::move(cmakeFilesOther));
 }
 
-void ServerModeReader::updateCodeModel(CppTools::RawProjectParts &rpps)
+CppTools::RawProjectParts ServerModeReader::createRawProjectParts() const
 {
+    CppTools::RawProjectParts rpps;
+
     int counter = 0;
     for (const FileGroup *fg : qAsConst(m_fileGroups)) {
         // CMake users worked around Creator's inability of listing header files by creating
@@ -399,6 +401,8 @@ void ServerModeReader::updateCodeModel(CppTools::RawProjectParts &rpps)
                                             : CppTools::ProjectPart::Library);
         rpps.append(rpp);
     }
+
+    return rpps;
 }
 
 void ServerModeReader::handleReply(const QVariantMap &data, const QString &inReplyTo)