As my Mac knowledge is limited I added some additional reviews. Any input is welcome

LGTM, did not checked though, in my opinion the minimal supported version should be the minimum target supported by Qt itself because most of the libs here are built mainly as dependencies for Qt / KDE apps, and settings something other than what Qt expect would not be good.

In D15374#322879, @fazevedo wrote:

LGTM, did not checked though, in my opinion the minimal supported version should be the minimum target supported by Qt itself because most of the libs here are built mainly as dependencies for Qt / KDE apps, and settings something other than what Qt expect would not be good.

Hm sounds logical.
Qmake doesn't offer a -query keyword for this, does it? 😛

In D15374#322937, @vonreth wrote:

In D15374#322879, @fazevedo wrote:

LGTM, did not checked though, in my opinion the minimal supported version should be the minimum target supported by Qt itself because most of the libs here are built mainly as dependencies for Qt / KDE apps, and settings something other than what Qt expect would not be good.

Hm sounds logical.
Qmake doesn't offer a -query keyword for this, does it? 😛

As we build stuff before that it wouldn't help. Hm but yes we should align with QT.

Unfortunately, no qmake does not provide that info AFAIK.

Given that Qt is likely to increase the dependency version rather than decrease it, could we check what it targets now and use that as a baseline for now (and revise it later if needed)?

While hardcoding is generally a bad thing we don't have much choice in this case as we will need to be building things before Qt is available.

According to http://doc.qt.io/qt-5/supported-platforms.html the minimum version is 10.11 so this should be fine.
As long as we update this version whenever Qt doesn't build keeping it in sync shouldn't be too difficult.
I also don't think it would be a problem if the minimum supported macos version for other software is lower than the Qt minimum.

Thanks for landing these fixes. Unfortunately it seems that libffi was either already broken or is now unhappy :(
https://binary-factory.kde.org/view/MacOS/job/Elisa_Nightly_macos/176/console

(I've purged the installation so this is definitely a fresh build)