scons: Allow GNU assembler version strings with hyphen
scons: Allow GNU assembler version strings with hyphen

Make scons a bit more forgiving when determining the GNU assembler version.
(transplanted from 0421e52a57af3340b16ad10d828ab186d4a3f345)

andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin