usage: build-mspgcc install

build-mspgcc downloads, extracts, builds, and installs binutils, gcc,
and libc for the TI MSP430 microcontroller.  As root, run:

  ./build-mspgcc install

The default installation directory is /opt/msp430.  Change this by
setting the environment variable INSTALL_DIR before compiling and
installing:

  INSTALL_DIR=/usr/local/msp430 ./build-mspgcc install
