Remove using iOS as SDKROOT (#7)

Author: DivineDominion

ReSwift-Thunk.xcodeproj/project.pbxproj

@@ -302,7 +302,6 @@
 				ONLY_ACTIVE_ARCH = YES;
 				PRODUCT_NAME = ReSwift_Thunk;
 				RESOURCES_TARGETED_DEVICE_FAMILY = "";
-				SDKROOT = iphoneos;
 				SUPPORTED_PLATFORMS = "iphonesimulator iphoneos watchsimulator watchos appletvsimulator appletvos macosx";
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
@@ -372,7 +371,6 @@
 				MTL_FAST_MATH = YES;
 				PRODUCT_NAME = ReSwift_Thunk;
 				RESOURCES_TARGETED_DEVICE_FAMILY = "";
-				SDKROOT = iphoneos;
 				SUPPORTED_PLATFORMS = "iphonesimulator iphoneos watchsimulator watchos appletvsimulator appletvos macosx";
 				SWIFT_COMPILATION_MODE = wholemodule;
 				SWIFT_OPTIMIZATION_LEVEL = "-O";