ProjectExplorer: Give build systems a name

... and make it accessible through a variable.

Fixes: QTCREATORBUG-26147
Change-Id: I0601c09a74360b91fe8421876207a8f4ae9d75b6
Reviewed-by: hjk <hjk@qt.io>

src/plugins/python/pythonproject.cpp

@@ -69,6 +69,7 @@ public:
     bool renameFile(Node *,
                     const Utils::FilePath &oldFilePath,
                     const Utils::FilePath &newFilePath) override;
+    QString name() const override { return QLatin1String("python"); }
 
     bool saveRawFileList(const QStringList &rawFileList);
     bool saveRawList(const QStringList &rawList, const QString &fileName);