Cross toolchain PKGBUILDs for Arch Linux

To build these packages you MUST provide a TARGET variable to makepkg like so:

TARGET=s390x makepkg or export TARGET=aarch64 before running makepkg

Build order: ${TARGET}-binutils -> ${TARGET}-linux-api-headers -> ${TARGET}-gcc (bootstrap) -> ${TARGET}-glibc (staging) -> ${TARGET}-gcc (staging) -> ${TARGET}-glibc -> ${TARGET}-gcc

The crossed packages can be created seperatly after the installation of the cross compiler toolchain.