How to use a create a cross compiler for Linux

Download and unpack

binutils - http://gnuftp.uib.no/binutils
gcc - http://gnuftp.uib.no/gcc/
gmp (dependency for gcc) - http://gnuftp.uib.no/gmp/
mpfr (dependency for gcc) - http://gnuftp.uib.no/mpfr/
mpc (dependency for gcc) - http://gnuftp.uib.no/mpc/
isl (OPTIONAL dependency for gcc) http://isl.gforge.inria.fr/

cd gcc-*
ln -s ../gmp-* gmp
ln -s ../mpfr-* mpfr
ln -s ../mpc-* mpc
ln -s ../isl-* isl

export TARGET=arm-linux-gnueabihf && export KERNEL_ARCH=arm
	or
export TARGET=s390x-unknown-linux && export KERNEL_ARCH=s390

mkdir /tmp/binutils-obj
cd /tmp/binutils-obj
#without glibc
${HOME}/binutils-*/configure --prefix=/opt/cross --target=${TARGET}
#with glibc
${HOME}/binutils-*/configure --prefix=/opt/cross --target=${TARGET} --with-sysroot=/opt/cross/sysroot.${TARGET}
make -j$(nproc)
make install-strip -j4

#without glibc - and only support for C
mkdir /tmp/gcc-obj
cd /tmp/gcc-obj
${HOME}/gcc-*/configure --prefix=/opt/cross --libexecdir=/opt/cross/lib --target=${TARGET} --enable-languages=c
make all-gcc -j$(nproc)
make install-strip-gcc -j4

# now you can compile the linux kernel

make ARCH=${KERNEL_ARCH} O=/tmp/kernel.build defconfig
make ARCH=${KERNEL_ARCH} O=/tmp/kernel.build CROSS_COMPILE=${TARGET}- -j$(nproc)

#with glibc
# Here we have a chicken/egg problem. glibc needs libgcc in order to compile, and libgcc needs glibc. But there is a hack.

mkdir /tmp/gcc-stage1
cd /tmp/gcc-stage1
${HOME}/gcc-*/configure --prefix=/opt/cross --libexecdir=/opt/cross/lib --target=${TARGET} --enable-languages=c --disable-threads --disable-shared
make all-gcc all-target-libgcc -j$(nproc)
make install-strip-gcc install-strip-target-libgcc -j4


cd ~/linux*/
make ARCH=${KERNEL_ARCH} O=/tmp/kernel.build INSTALL_HDR_PATH=/opt/cross/sysroot.${TARGET}/usr headers_install

#glibc
mkdir /tmp/glibc-stage1
cd /tmp/glibc-stage1
~/glibc/configure --prefix=/usr --host=${TARGET} --with-headers=/opt/cross/sysroot.${TARGET}/usr/include
make -j$(nproc)
make install DESTDIR=/opt/cross/sysroot.${TARGET}

mkdir /tmp/gcc-stage2
cd /tmp/gcc-stage2
${HOME}/gcc-*/configure --prefix=/opt/cross --libexecdir=/opt/cross/lib --target=${TARGET} --enable-languages=c,c++ --with-sysroot=/opt/cross/sysroot.${TARGET}
make -j$(nproc)
make install-strip -j4

#try with glibc now
mkdir /tmp/glibc-stage2
cd /tmp/glibc-stage2
~/glibc/configure --prefix=/usr --host=${TARGET}
make -j$(nproc)

make install DESTDIR=/opt/cross/sysroot.${TARGET}




Now you can move $(pwd)/dest/${TARGET} where ever you want.

If you are sparse on disk space you can trim it a bit as well 

$ rm -rf dest/*/{include,share} dest/*/lib/libcc*
$ find dest -name '*.la' -delete
$ find dest -name "*.a" -exec ./dest/*/bin/*-strip -g "{}" \;

Notes

BSD and MacOS.
This will most probably work if you use gmake instead of make.

Git
If you get your sources with git, you'll also need flex, bison and makeinfo (texinfo).

GMP, MPFR, MPC and ISL
You can skip this if you already have them installed. They are not target libraries.
Keep in mind that you need both the libraries and the headers installed in order to use them. In some distributions that means
that you also need to have the -dev or -devel packages installed.