Keep 32-bit build support on Mojave

[Joshua Root]

On 2018-9-24 18:22 , Ryan Schmidt wrote:
> https://github.com/ryandesign/macports-base/commits/MacOSX.sdk

Looks mostly reasonable, but there are a couple of issues.

First, configure_get_sdkroot is the wrong place to register a callback,
since it can easily be called multiple times. The callback should be
registered once, unconditionally, and should add the dependency only if
the SDK doesn't exist (or if it's an SDK that normally wouldn't exist?
There is still a dependency on the SDK port even if it's already installed).

Second, I'm not sure about changing the SDK only some of the time, or
not changing the deployment target. We've always recommended changing
the deployment target for an entire installation globally if it's going
to be changed, and Apple only supports using a deployment target <= the
SDK being used. If it was only the i386 slices that were built against a
different SDK, that would be different, but the x86_64 slices of
universal builds will also be built against a different SDK than
non-universal x86_64 ports. A non-universal port built against the 10.14
SDK could thus end up linked with a universal port built against the
10.13 SDK.

I'm not sure how much of a problem all that is. It's unknown territory.

- Josh