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/cmakeprojectmanager/cmakebuildsystem.h

@@ -67,6 +67,7 @@ public:
                   const Utils::FilePaths &filePaths, Utils::FilePaths *) final;
 
     Utils::FilePaths filesGeneratedFrom(const Utils::FilePath &sourceFile) const final;
+    QString name() const final { return QLatin1String("cmake"); }
 
     // Actions:
     void runCMake();