t6000lib: workaround a possible dash bug

t6000lib: workaround a possible dash bug

pdksh doesn't need this patch, of course bash works fine since
that what most users use.

Normally, 'var=val command' seems to work fine with dash, but
perhaps there's something weird going on with "$@".  dash is
pretty widespread, so it'll be good to support this even though
it does seem like a bug in dash.

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>