For Building XNU 16.7 from start to finish Requirements macOS 10.12.6 and Xcode 8.3.3
These must be done in order or it will not build
Open terminal.app // copy each command in as you go.
Creating workspace
mkdir -p ~/Desktop/xnu_build
cd ~/Desktop/xnu_build
curl -O https://opensource.apple.com/tarballs/dtrace/dtrace-209.50.12.tar.gz &&
curl -O https://opensource.apple.com/tarballs/AvailabilityVersions/AvailabilityVersions-26.50.4.tar.gz &&
curl -O https://opensource.apple.com/tarballs/xnu/xnu-3789.70.16.tar.gz &&
curl -O https://opensource.apple.com/tarballs/libdispatch/libdispatch-703.50.37.tar.gz &&
curl -O https://opensource.apple.com/tarballs/libplatform/libplatform-126.50.8.tar.gz
for file in *.tar.gz; do tar -zxf $file; done && rm -f *.tar.gz
cd dtrace-209.50.12
mkdir -p obj sym dst
xcodebuild install -target ctfconvert -target ctfdump -target ctfmerge ARCHS="x86_64" SRCROOT=$PWD OBJROOT=$PWD/obj SYMROOT=$PWD/sym DSTROOT=$PWD/dst
sudo ditto $PWD/dst/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain
cd ../AvailabilityVersions-26.50.4/
mkdir -p dst
make install SRCROOT=$PWD DSTROOT=$PWD/dst
sudo ditto $PWD/dst/usr/local `xcrun -sdk macosx -show-sdk-path`/usr/local
cd ../xnu-3789.70.16/
mkdir -p BUILD.hdrs/obj BUILD.hdrs/sym BUILD.hdrs/dst
make installhdrs SDKROOT=macosx ARCH_CONFIGS=X86_64 SRCROOT=$PWD OBJROOT=$PWD/BUILD.hdrs/obj SYMROOT=$PWD/BUILD.hdrs/sym DSTROOT=$PWD/BUILD.hdrs/dst
sudo xcodebuild installhdrs -project libsyscall/Libsyscall.xcodeproj -sdk macosx ARCHS='x86_64 i386' SRCROOT=$PWD/libsyscall OBJROOT=$PWD/BUILD.hdrs/obj SYMROOT=$PWD/BUILD.hdrs/sym DSTROOT=$PWD/BUILD.hdrs/dst
sudo ditto BUILD.hdrs/dst `xcrun -sdk macosx -show-sdk-path`
cd ../libplatform-126.50.8
sudo ditto $PWD/include `xcrun -sdk macosx -show-sdk-path`/usr/local/include
cd ../libdispatch-703.50.37
mkdir -p BUILD.hdrs/obj BUILD.hdrs/sym BUILD.hdrs/dst
sudo xcodebuild install -project libdispatch.xcodeproj -target libfirehose_kernel -sdk macosx ARCHS='x86_64 i386' SRCROOT=$PWD OBJROOT=$PWD/obj SYMROOT=$PWD/sym DSTROOT=$PWD/dst
sudo ditto $PWD/dst/usr/local `xcrun -sdk macosx -show-sdk-path`/usr/local
cd ../xnu-3789.70.16/
make SDKROOT=macosx ARCH_CONFIGS=X86_64 KERNEL_CONFIGS=RELEASE