BR_SOURCE_DIR	Root of source tree				Required
BR_MAKE_DIR	Makefile directory				Required
BR_TARGET_DIR	Target directory				Required
BR_MAKEFILE	Makefile to use					Required

BR_LONG_ARGS	Use response files for long argument lists	Optional
BR_LIB_SUFFIX	Extra suffixes for library name			Optional

BR_BUILD	Type of build - DEBUG, RELEASE, PROFILE, TEST	Optional (Default = RELEASE)
BR_EXTENDER	DOS extender to target				Optional

BR_BASE_TYPE	Type to build library with - FIXED ot FLOAT	Optional (Default = FIXED)