Add improved support for simple iOS sticker packs (#824)

* Allow messages applications to skip the compile sources phase

By default, simple iOS sticker packs created in Xcode do not include
a compile sources phase. This change will allow messages applications
with an empty list of sources to skip that phase entirely.

* Add support for launchAutomaticallySubstyle in run schemes

This is especially important for simple iOS sticker packs that require
this run scheme setting to be set to 2 in order to run the scheme
properly.

Sources/XcodeGenKit/PBXProjGenerator.swift

@@ -927,9 +927,7 @@ public class PBXProjGenerator {
         }
 
         let sourcesBuildPhaseFiles = getBuildFilesForPhase(.sources)
-        // Sticker packs should not include a compile sources build phase as they
-        // are purely based on a set of image files, and nothing else.
-        let shouldSkipSourcesBuildPhase = sourcesBuildPhaseFiles.isEmpty && target.type == .stickerPack
+        let shouldSkipSourcesBuildPhase = sourcesBuildPhaseFiles.isEmpty && target.type.canSkipCompileSourcesBuildPhase
         if !shouldSkipSourcesBuildPhase {
             let sourcesBuildPhase = addObject(PBXSourcesBuildPhase(files: sourcesBuildPhaseFiles))
             buildPhases.append(sourcesBuildPhase)

Sources/XcodeGenKit/SchemeGenerator.swift

@@ -241,7 +241,8 @@ public class SchemeGenerator {
             commandlineArguments: launchCommandLineArgs,
             environmentVariables: launchVariables,
             language: scheme.run?.language,
-            region: scheme.run?.region
+            region: scheme.run?.region,
+            launchAutomaticallySubstyle: scheme.run?.launchAutomaticallySubstyle
         )
 
         let profileAction = XCScheme.ProfileAction(