Current Version: cctools: 1009.2, ld64: 907.
Originally ported by cjacker.

SUPPORTED HOST OPERATING SYSTEMS:

Linux, FreeBSD, OpenBSD,
macOS, iOS

SUPPORTED HOST ARCHITECTURES:

x86, x86_64, arm, arm64/AArch64, PowerPC/PowerPC64

armv6, armv7, armv7s, arm64, arm64e,
arm64_32 (untested), i386, x86_64, x86_64h,
armv6m, armv7k, armv7m and armv7em

arm64e requires Apple LLVM/Clang.

macOS, iOS, tvOS, watchOS, bridgeOS, Mac Catalyst,
iOS Simluator, watchOS Simulator, DriverKit

Not all of the targets have been tested.

Clang 10
libstdc or libc with C 20 support; depending on what your compiler uses
libdispatch-dev and libblocksruntime (the runtime should be installed by the dispatch library)

SDKs with .tdb stubs (>= Xcode 7) require the TAPI library to be installed.
=> https://github.com/tpoechtrager/apple-libtapi

musl-libc based systems require the musl-fts library to be installed. => https://github.com/pullmoll/musl-fts

Kind of optional, but highly recommended:

llvm >= 13 (For llvm-otool, otherwise there is no otool support)

Optional, but recommended:

llvm-devel (For Link Time Optimization Support)
uuid-devel (For ld64 -random_uuid Support)
llvm-devel xar-devel (For ld64 -bitcode_bundle Support)

You can find xar here.
Do not install libxar-dev on Ubuntu, it's a different package.

This step is only required if you intend to use SDKs with .tdb stubs.

git clone https://github.com/tpoechtrager/apple-libtapi.git
cd apple-libtapi
[INSTALLPREFIX=/home/user/cctools] ./build.sh
./install.sh

git clone https://github.com/tpoechtrager/cctools-port.git
cd cctools-port/cctools
./configure \
    [--prefix=/home/user/cctools] \
    [--with-libtapi=/home/user/cctools] \
    [--target=<target>] \
    [--with-llvm-config=...]
make
make install

target = i386-apple-darwin11, x86_64-apple-darwin11, arm-apple-darwin11, ...