For windows it is “easy” as https://docs.unrealengine.com/latest/INT/Programming/Development/ManagingGameCode/index.html#generatingprojectfiles but what about XCode project and you only have uproject file? the engine cant start the project because it need that the project is compiled before from source.
Just found it on the next match of the search https://forums.unrealengine.com/showthread.php?68609-Compiling-windows-project-on-OSX-quot-The-following-modules-are-missing-or-built-with-a-different-quot&p=282971&viewfull=1#post282971 basically there is right click->services->generate xcode project.
Still I get
Discovering modules, targets and source code for game... Generating data for project indexing... 0%Compiling with non-standard Xcode (xcode-select): /Library/Developer/CommandLineTools/ Triggered an exception while looking for SDK directory in Xcode.app System.IO.DirectoryNotFoundException: Directory '/Library/Developer/CommandLineTools/Platforms/MacOSX.platform/Developer/SDKs' not found. at System.IO.Directory.ValidateDirectoryListing (System.String path, System.String searchPattern, System.Boolean& stop) [0x00000] in <filename unknown>:0 at System.IO.Directory.GetFileSystemEntries (System.String path, System.String searchPattern, FileAttributes mask, FileAttributes attrs) [0x00000] in <filename unknown>:0 at System.IO.Directory.GetDirectories (System.String path, System.String searchPattern) [0x00000] in <filename unknown>:0 at System.IO.Directory.GetDirectories (System.String path) [0x00000] in <filename unknown>:0 at UnrealBuildTool.AppleToolChain.SelectSDK (System.String BaseSDKDir, System.String OSPrefix, System.String& PlatformSDKVersion, Boolean bVerbose) [0x00000] in <filename unknown>:0 ERROR: Invalid SDK MacOSX.sdk, not found in /Library/Developer/CommandLineTools/Platforms/MacOSX.platform/Developer/SDKs
Well, apparently UE4 doesnt like beta versions of XCode, I have installed a xcode-beta, so I downloaded the latest stable.