Compiling for older versions of Mac OS X

I have recently started producing applications for the Mac, on my most recent release I got overwhelming suggestions to get the app working on OSX 10.5 as I'm working in and compiling for 10.6.

I tried looking for the 10.5 SDK but couldn't find it anywhere to download! How can I go about compiling my app for older versions of Mac OS X using Xcode 2.2 and developing in 10.6?

EDIT: ------ I will mention I don't have the to option to select different SDKs as I don't have any others installed and my problem is more not being able to find where to get those sdks开发者_如何学C from? then actually not know how to go about compiling for the older sdks

Redownload the entire Xcode Tools packages from http://developer.apple.com/mac/. Then, run the installer, and when you get to the screen that says "Standard Install", instead of pressing Continue, press Customize in the bottom left-hand corner. You should have the option to install MacOSX10.5.sdk as well as MacOSX10.4u.sdk.

This can be configured in the project or target settings (right-click -> Get Info):

Build -> Base SDK.

Downloading other SDKs didn't work fo me. What helped is just setting:

Build Settings -> MACOSX_DEPLOYMENT_TARGET

to desired OSX version in Project Editor. It worked with the default SDK.

Xcode 10.3, Dev. OS: 10.14 (Mojave), Deployment OS: 10.13 (High Sierra)