The generator causes segfaults because it doesn't call pkg_init()
- Do the initialization (to be submitted upstream) and related work.
- Introduce port OPTION to re-enable the generator (not by default, because it still fails stage-qa because of libarchive).
This still needs additional work because the case of the resulting
package is incorrect (e.g. produces file called Cmake-3.1.13.tgz,
but then tries copying cmake-3.1.13.tgz).