macosx_deployment_target - building for previous versions from MacOS 10.13

[Friedrich Beckmann]

Hi,

i use macports to build a MacOS application bundle for the pspp statistics software. I build on my Macbook with MacOS 10.13 and XCode 10.1. The idea is that the bundle can run also on previous MacOS versions. I do this by setting the macosx_deployment_target to 10.8 in macports.conf. As this usually gives problems with some ports, e.g. now rust:

https://github.com/macports/macports-ports/pull/8259

I switched to the plan to only compile the library dependencies of pspp with a different deployment target. So I install everything with no deployment target, then I force uninstall some ports, enable deployment target and install those ports again. So I try to avoid to compile build time dependencies like gimp and rust with a different deployment target. This seems to work.

Now I wanted to go further down and set the deployment target to 10.5. It seems that the XCode 10.1 compiler then does not compile C++ anymore, e.g. when compiling ncurses. Does anybody know some description or a strategy how to compile for previous MacOS versions with macports? 

Can I for example compile with a GNU gcc compiler and the deployment target is still honoured?

Friedrich