Hello and my first question (regarding CMAKE_OSX_DEPLOYMENT_TARGET)

[Michael Monschau]

Hi Everyone,

I am fairly new to macports. I build and license development software for a niche marked (I develop plugin tools for the RAD Development Tool Omnis Studio). I am based in the UK.

Background:
I recently had the need to resort to some open software to add certain PDF manipulation features to one of my products. The open source tool I am using is podofo-0.9.7. That uses various other libraries including openssl. As part of my own XCode project I have to link against crypto.dylib (linking against the crypto.a library in XCode). 
Note: I am using 'port install' with the ‘+universal’ flag as I need universal libraries

The problem:
I am building the macports libraries that I need on macOS 11.4. However, I need the deployment target for my own xcode projects to be 10.13 and to avoid hundreds of link warnings which may push out important ones, I need to rebuild openssl with that deployment target set. I understand there is CMAKE_OSX_DEPLOYMENT_TARGET and I can do set(CMAKE_OSX_DEPLOYMENT_TARGET “10.13”), but I don’t know
     1. where I do this (I was thinking in '/opt/local/share/cmake-3.20/Modules/Platform/Darwin.cmake' but not sure)
     2. how to force the rebuilding from source using cmake of the openssl libraries via 'port install'

Many thanks for any answers that yo can provide

Kind regards,
Michael

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