I have XCode 16.4 installed with macOS SDK 15.5. When building using that SDK, what is the oldest/minimum supported value for -mmacosx-version-min? Specifically, is -mmacosx-version-min=11.0 still supported? Also, has it been announced for macOS 26 what the oldest/minimum supported value will be for -mmacosx-version-min? Specifically, will -mmacosx-version-min=11.0 still be supported? Where would this be documented?

I am an aspiring developer and have not coded for macOS before. I would like to install libgimp-2.0dev so that I can learn how to write a C plugin for gimp, which I am running in macOS. I can manage installing a library using apt-get in Ubuntu but apt-get doesn't seem to be available in macOS. How would I go about installing this library in macOS so that I can code for it in Xcode?