Refactoring in commit v3.7.0-rc1~523^2 (CPack/PackageMaker: port to
cmXMLWriter, 2016-06-08) accidentally broke `distribution.dist`
generation when there are dependencies between components and the pkg
(or the derived productbuild) generator are used. The resulting
package cannot be installed and instead the Apple Installer app
shows a "Javascript error" message.
The problem is that a `std::ostringstream` is constructed with some
content, but the stream pointer still points to the beginning of the
stream, so subsequent writes overwrite the initial content instead of
appending.