Utils: Introduce a FilePath::withNewPath() convenience method

It's effectively the mirrored version of onDevice() with an
equally odd name which is a bit more straightforward to use
in some cases.

Change-Id: I0cfedeb58871a857c93144e2a0d734bad1bcd887
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/cmakeprojectmanager/cmaketoolmanager.cpp

@@ -185,7 +185,7 @@ void CMakeToolManager::autoDetectCMakeForDevice(const FilePath &deviceRoot,
                                                 QString *logMessage)
 {
     QStringList messages{tr("Searching CMake binaries...")};
-    const FilePaths candidates = {FilePath::fromString("cmake").onDevice(deviceRoot)};
+    const FilePaths candidates = {deviceRoot.withNewPath("cmake")};
     const Environment env = deviceRoot.deviceEnvironment();
     for (const FilePath &candidate : candidates) {
         const FilePath cmake = candidate.searchOnDevice(env.path());