[coreboot] Crosscompiler script

[Patrick Georgi]

Hi,

after the recent troubles with various compilers miscompiling coreboot,
we decided to publish the script we use to build the compiler we use at
coresystems.
It requires a gnu compatible tar, gnu patch, wget and probably has
other, hidden dependencies on behaviour as found on Linux and Mac OS X.

Running buildgcc downloads the tarballs (tarball subdirectory), patches
the trees slightly (the attached patches must reside in the same
directory), links them together (in a totally unsupported but working
way), and builds and installs the toolchain (into $PWD/xgcc).
Add $PWD/xgcc/bin to your PATH, abuild should pick up the crosscompiler
automatically.

Regards,
Patrick