Fixed couple script errors and added error checking

Added error checking to each part of the build and stop on the first
component that fails to build.

Create $COMPILE_DIR if it does not exist.

Added missing fi to and if-else block.
Added options to control build script

Individual tools in the build/install script for the AVR tools can be
selected as needed with the default being all tools but uisp.  Also, the
install prefix can be selected from the command-line without modifying
the script.