add support for ctors/dtors on arm with modern gcc

add support for ctors/dtors on arm with modern gcc

a while back, gcc switched from using the old _init/_fini fragments
method for calling ctors and dtors on arm to the __init_array and
__fini_array method. unfortunately, on glibc this depends on ugly
hacks involving making libc.so a linker script and pulling parts of
libc into the main program binary. so I cheat a little bit, and just
write asm to iterate over the init/fini arrays from the _init/_fini
asm. the same approach could be used on any arch it's needed on, but
for now arm is the only one.