build_helper_configs.py: Switch config_debug to GNUARM

GNUARM is more mature, more well-known toolchain which is easier to
install for local testing.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I54e885003b554707dcb2c6f727552f7e6e9b6794
1 file changed