Lack of alignment causes minix_stack_fill to produce an incorrect
frame layout, subsequently resulting in a crash of the started
process. For now, we assume that the other callers of
minix_stack_fill do get an aligned buffer through sbrk(3), but this
may have to be changed later as well.
Change-Id: I1575bd62b050749d1a1aae7417310c91713462c3
65c4b82f02