CMake: Split build output into lines before parsing

This amends commit b15d1951a2, where we moved the line splitting into
the output parsers, but overlooked that the CMakeBuildStep does
additional line-based parsing. As a result, the stdout -> stderr
redirection for ninja output was broken.

Change-Id: Iafbbce9a3f9c0383812a9e4c129c1d94fa907b73
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/cmakeprojectmanager/cmakebuildstep.h

@@ -77,7 +77,7 @@ protected:
     bool fromMap(const QVariantMap &map) override;
 
     // For parsing [ 76%]
-    void stdOutput(const QString &line) override;
+    void stdOutput(const QString &output) override;
 
 private:
     void ctor(ProjectExplorer::BuildStepList *bsl);