Changing default cxx_stdlib to libc++

[Ryan Schmidt]

On Mar 10, 2018, at 11:06, Kenneth F. Cunningham wrote:

> However, at some point in the next few months, when most of the dust has settled and most or all of the available binaries are all properly built against libc++, I'll change the single line in macports.conf from "buildfromsource always" to "buildfromsource if needed" , and get some prebuilt binaries. This will be nice for the real big ones, like octave and llvm and clang and qt4 etc.

If you set up this installation by following the LibcxxOnOlderSystems instructions, and you set "delete_la_files yes" as it says to do, then you will not be able to use the libc++ binaries we generate, because our binaries for 10.8 and earlier are generated with "delete_la_files no", and the same "delete_la_files" setting must be used by all of the ports that depend upon one another.