The GNU .init_array support is an extension over the standard System V
ABI .init_array support, which passes the main() arguments to the init
function.

This support comes in three parts. First the dynamic linker (from glibc)
needs to support it. Then function pointers need to be placed in the
section, for example by using __attribute__((constructor)), that the
compiler (gcc or clang for example) might place in section .ctors and
the linker (from binutils) will move to .init_array on the output
object, or by placing them directly into .init_array by the compiler
when compiling. If this does not happen and the function pointers end
up in .ctors, then they will not get passed the main() arguments, which
we do really need in this case.

But this relies on recent binutils or gcc having native .init_array
support, and not having it disabled through --disable-initfini-array.

To guarantee we get the correct behaviour, let's just place the function
pointer in the .init_array section directly, so we only require a recent
enough glibc.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=65029