elf: initialize init_table to zero, ensure TLS is found

If the ELF code is unable to find the PT_TLS section,
complain loudly and fail.

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
build.mk: aarch64: don't destroy the instruction at offset 0x10

this caused a lot of self-inflicted pain.

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>