buildman: improve readability of toolchain check
buildman: fix toolchain priority_list

'-elf' appears twice in the toolchain priority_list.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
patman, buildman: avoid using magic numbers in code

When changing the foreground color, '+30' is a magic number.
Put it into the BRIGHT_START and NORMAL_START macros.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>