ProjectExplorer: Provide the option to build only the app to be run

... instead of the entire project.
This can speed up the development cycle by ignoring irrelevant changes
in the project, potentially at the cost of missing parts that actually
should be re-built (in particular with build systems where a product
does not have full knowledge of its dependencies).
Supported by qmake and qbs for now.

Change-Id: Ic7101aa243e92ba139798d13366d256c1919dcc3
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/qmakeprojectmanager/qmakebuildconfiguration.cpp

@@ -886,4 +886,15 @@ bool QmakeBuildConfiguration::regenerateBuildFiles(Node *node)
     return true;
 }
 
+void QmakeBuildConfiguration::restrictNextBuild(const RunConfiguration *rc)
+{
+    if (!rc) {
+        setSubNodeBuild(nullptr);
+        return;
+    }
+    const auto productNode = dynamic_cast<QmakeProFileNode *>(rc->productNode());
+    QTC_ASSERT(productNode, return);
+    setSubNodeBuild(productNode);
+}
+
 } // namespace QmakeProjectManager