This build setting is actually relative to the Derived Data setting.
You can change this setting if you go to Xcode > Preferences > Locations, and change the Derived Data directory setting to whatever suits your needs (Default, Relative or Custom).

You can also specify this on a per project-basis, if you specify an absolute path for that settings:
- You can either hardcode a path such as
/build/${CONFIGURATION}${EFFECTIVE_PLATFORM_NAME}
, then the project will be built into the folder build in the root folder.
- Or can you can choose to prepend the existing path with another environment variable. For example, to make the path relative to your project/workspace (As you would expect), you can prepend the original value with
${SRCROOT}/
, effectively creating a build
folder at the root of your project/workspace.
Settings that can be substitued in ${<setting>}
are called Build settings, and are set automatically by Xcode/xcodebuild whenever you start building your project. Apple maintains a list of the available build settings here:
http://help.apple.com/xcode/mac/8.0/#/itcaec37c2a6