This is xnu-8019. See this file in:
#include "<DEVELOPER_DIR>/Makefiles/CoreOS/Xcode/BSD.xcconfig"

BUILD_VARIANTS = normal
SUPPORTED_PLATFORMS = macosx iphoneos iphoneosnano tvos appletvos watchos bridgeos
ONLY_ACTIVE_ARCH = NO
DEAD_CODE_STRIPPING = YES
DEBUG_INFORMATION_FORMAT = dwarf-with-dsym

SDK_INSTALL_VARIANT = $(SDK_INSTALL_VARIANT_$(DRIVERKIT))
SDK_INSTALL_VARIANT_1 = driverkit
SDK_INSTALL_VARIANT_ = default
SDK_INSTALL_ROOT = $(SDK_INSTALL_ROOT_$(SDK_INSTALL_VARIANT))
SDK_INSTALL_ROOT_driverkit = $(DRIVERKITROOT)
SDK_INSTALL_HEADERS_ROOT = $(SDK_INSTALL_HEADERS_ROOT_$(SDK_INSTALL_VARIANT))
SDK_INSTALL_HEADERS_ROOT_driverkit = $(SDK_INSTALL_ROOT)/$(SDK_RUNTIME_HEADERS_PREFIX)
SDK_RUNTIME_HEADERS_PREFIX = Runtime

INSTALL_PATH = $(SDK_INSTALL_ROOT)/usr/lib/system
PUBLIC_HEADERS_FOLDER_PATH = $(SDK_INSTALL_HEADERS_ROOT)/usr/include
PRIVATE_HEADERS_FOLDER_PATH = $(SDK_INSTALL_HEADERS_ROOT)/usr/local/include
OS_PRIVATE_HEADERS_FOLDER_PATH = $(SDK_INSTALL_HEADERS_ROOT)/usr/local/include/os
OS_PUBLIC_HEADERS_FOLDER_PATH = $(SDK_INSTALL_HEADERS_ROOT)/usr/include/os
EXECUTABLE_PREFIX = libsystem_
PRODUCT_NAME = kernel
ALWAYS_SEARCH_USER_PATHS = NO
OTHER_CFLAGS = -fdollars-in-identifiers -no-cpp-precomp -fno-common -fno-stack-protector -fno-stack-check -momit-leaf-frame-pointer -DLIBSYSCALL_INTERFACE -D__DARWIN_VERS_1050=1 -DNO_SYSCALL_LEGACY
OTHER_CFLAGS[sdk=macosx*][arch=i386] = $(inherited) -UNO_SYSCALL_LEGACY -DSYSCALL_PRE1050
OTHER_CFLAGS[sdk=macosx*][arch=x86_64*] = $(inherited) -DSYSCALL_PRE1050
GCC_PREPROCESSOR_DEFINITIONS = CF_OPEN_SOURCE CF_EXCLUDE_CSTD_HEADERS DEBUG _FORTIFY_SOURCE=0

HEADER_SEARCH_PATHS = $(PROJECT_DIR)/mach $(PROJECT_DIR)/os $(PROJECT_DIR)/wrappers $(PROJECT_DIR)/wrappers/string $(PROJECT_DIR)/wrappers/libproc $(PROJECT_DIR)/wrappers/libproc/spawn $(BUILT_PRODUCTS_DIR)/internal_hdr/include $(BUILT_PRODUCTS_DIR)/mig_hdr/local/include $(BUILT_PRODUCTS_DIR)/mig_hdr/include
SYSTEM_HEADER_SEARCH_PATHS = $(SDKROOT)/$(SDK_INSTALL_HEADERS_ROOT)/System/Library/Frameworks/System.framework/PrivateHeaders $(SDKROOT)/$(SDK_INSTALL_HEADERS_ROOT)/usr/local/include $(SDKROOT)/$(SDK_INSTALL_HEADERS_ROOT)/usr/include
SYSTEM_FRAMEWORK_SEARCH_PATHS = $(SDKROOT)/$(SDK_INSTALL_HEADERS_ROOT)/System/Library/Frameworks

OTHER_MIGFLAGS = -novouchers -I$(SDKROOT)/$(SDK_INSTALL_HEADERS_ROOT)/System/Library/Frameworks/System.framework/PrivateHeaders -I$(SDKROOT)/$(SDK_INSTALL_HEADERS_ROOT)/usr/local/include -I$(SDKROOT)/$(SDK_INSTALL_HEADERS_ROOT)/usr/include

WARNING_CFLAGS = -Wmost
GCC_TREAT_WARNINGS_AS_ERRORS = YES
GCC_WARN_ABOUT_MISSING_NEWLINE = YES
GCC_NO_COMMON_BLOCKS = YES
GCC_C_LANGUAGE_STANDARD = gnu11
CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES
CLANG_WARN_EMPTY_BODY = YES
CLANG_WARN_BOOL_CONVERSION = YES
CLANG_WARN_CONSTANT_CONVERSION = YES
GCC_WARN_64_TO_32_BIT_CONVERSION = NO
CLANG_WARN_ENUM_CONVERSION = YES
CLANG_WARN_INT_CONVERSION = NO
CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES
CLANG_WARN_INFINITE_RECURSION = YES
GCC_WARN_ABOUT_RETURN_TYPE = YES
CLANG_WARN_STRICT_PROTOTYPES = YES
CLANG_WARN_COMMA = YES
GCC_WARN_UNINITIALIZED_AUTOS = YES
CLANG_WARN_UNREACHABLE_CODE = YES
GCC_WARN_UNUSED_FUNCTION = YES
GCC_WARN_UNUSED_PARAMETER = YES
GCC_WARN_UNUSED_VARIABLE = YES
CLANG_WARN_RANGE_LOOP_ANALYSIS = YES
CLANG_WARN_SUSPICIOUS_MOVE = YES

CODE_SIGN_IDENTITY = -
DYLIB_CURRENT_VERSION = $(RC_ProjectSourceVersion)
DYLIB_LDFLAGS = -umbrella System -all_load $(BUILT_PRODUCTS_DIR)/$(EXECUTABLE_PREFIX)$(PRODUCT_NAME).a
OTHER_LDFLAGS = $(SIMULATOR_LDFLAGS)
SIMULATOR_LDFLAGS =
SIMULATOR_LDFLAGS[sdk=macosx*] = -Wl,-simulator_support
INSTALLHDRS_SCRIPT_PHASE = YES
INSTALLHDRS_COPY_PHASE = YES
USE_HEADERMAP = NO
LINK_WITH_STANDARD_LIBRARIES = NO
ALWAYS_SEARCH_USER_PATHS = YES
IS_ZIPPERED = YES