[Build] Configure Xcode project to reference Precompiled Header. The .podspec changes aren't enough by themselves.

Author: appleguy

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -2157,6 +2157,8 @@
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				GCC_INSTRUMENT_PROGRAM_FLOW_ARCS = YES;
 				GCC_NO_COMMON_BLOCKS = YES;
+				GCC_PRECOMPILE_PREFIX_HEADER = YES;
+				GCC_PREFIX_HEADER = "AsyncDisplayKit/AsyncDisplayKit-Prefix.pch";
 				GCC_PREPROCESSOR_DEFINITIONS = "$(inherited)";
 				INFOPLIST_FILE = "$(SRCROOT)/AsyncDisplayKit/Info.plist";
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
@@ -2187,6 +2189,8 @@
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				GCC_INSTRUMENT_PROGRAM_FLOW_ARCS = NO;
 				GCC_NO_COMMON_BLOCKS = YES;
+				GCC_PRECOMPILE_PREFIX_HEADER = YES;
+				GCC_PREFIX_HEADER = "AsyncDisplayKit/AsyncDisplayKit-Prefix.pch";
 				INFOPLIST_FILE = "$(SRCROOT)/AsyncDisplayKit/Info.plist";
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";
@@ -2299,6 +2303,8 @@
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				GCC_INSTRUMENT_PROGRAM_FLOW_ARCS = NO;
 				GCC_NO_COMMON_BLOCKS = YES;
+				GCC_PRECOMPILE_PREFIX_HEADER = YES;
+				GCC_PREFIX_HEADER = "AsyncDisplayKit/AsyncDisplayKit-Prefix.pch";
 				INFOPLIST_FILE = "$(SRCROOT)/AsyncDisplayKit/Info.plist";
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Frameworks";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @loader_path/Frameworks";