Docker: Make mounted volumes user-configurable

Still use the so-far hardcoded "/opt" and "/data" as default, i.e.
not the intended final setup which should at least pick up
the source and build dirs automatically.

Change-Id: If632f3f5a6e824a952938c97336df8ff58b39d67
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/docker/dockerdevice.h

@@ -44,6 +44,7 @@ public:
     QString tag;
     QString size;
     bool useLocalUidGid = true;
+    QStringList mounts = {"/opt", "/data"};
 };
 
 class DockerDevice : public ProjectExplorer::IDevice
@@ -100,6 +101,7 @@ public:
     Utils::Environment systemEnvironment() const override;
 
     const DockerDeviceData &data() const;
+    DockerDeviceData &data();
 
     void tryCreateLocalFileAccess() const;
     bool hasLocalFileAccess() const;