Apple has released Xcode 4.3.1, an update of the set of developer tools for Mac OS X. The new version is compatible with iOS 5.1.

Xcode 4.3.1 also sports software development kits for Mac OS X 10.7 (“Lion”), as well as iOS 5.1. Other additions include a code signing workflow for for signing OS X apps with Developer IDs, an installer for command line tools, support for launching Instruments and File Merge from the Open Developer Tool menu, bug fixes, and more.

Xcode 4.3.1 requires Mac OS X 1.7.3 or higher. It’s a free download at the Mac App Store.