Building all ports when setting up a new buildbot builder

[Ryan Schmidt]

So after 99 hours, the Yosemite builder failed building "all" ports, with a memory error:

https://build.macports.org/builders/buildports-yosemite-x86_64/builds/71/steps/compile/logs/err.text

I think we should refrain from trying to build all 20,000 ports at once. It takes over a week anyway. We should instead build smaller sets of ports at a time. Since archives are not uploaded to the packages server until the entire set of ports has been built, building smaller sets of ports will let some packages become available sooner.

Here are some reasonably-sized chunks we could have the builder build:

$ port echo name:^[0-9a-d]|wc -l
    1120
$ port echo name:^[e-h]|wc -l
    1316
$ port echo name:^[i-l]|wc -l
    1319
$ port echo name:^[m-o]|wc -l
    1005
$ port echo name:^[q-s]|wc -l
    1115
$ port echo name:^[t-z]|wc -l
    1078
$ port echo name:^p[a-z]|wc -l
    5761
$ port echo name:^p[0-9]|wc -l
    7362

I am assuming that if we set the portlist to e.g. "name:^[0-9a-d]" instead of "all" that it would work.

Also, we should allow the current build of ~7000 ports to finish and upload, rather than interrupting that.