Enables APPLICATION_EXTENSION_API_ONLY build setting

Allows app extensions to link against AltSign without warnings.

Author: rileytestut

AltSign.xcodeproj/project.pbxproj

@@ -1157,6 +1157,7 @@
 		BF5AB3A22285FDB200DC914B /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CLANG_WARN_DOCUMENTATION_COMMENTS = NO;
 				CODE_SIGN_IDENTITY = "";
 				CODE_SIGN_STYLE = Manual;
@@ -1183,6 +1184,7 @@
 		BF5AB3A32285FDB200DC914B /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				APPLICATION_EXTENSION_API_ONLY = YES;
 				CLANG_WARN_DOCUMENTATION_COMMENTS = NO;
 				CODE_SIGN_IDENTITY = "";
 				CODE_SIGN_STYLE = Manual;