arm: Improve the creation of kernel.bin

[mmel]

Summary

Instead of relinking the kernel without elf headers, replace them with
a binary blob of the same length starting with a jump to the kernel's
start address. This ensures that all symbols stay at the same offsets
as in the original kernel, so kernel.debug remains valid also for
kernel.bin.
While I'm on, ensure that the awk script used runs with
the neutral locale defined. Awk 'write' is a locale compilant, and
script is used to write binary data to a file, so it needs to ensure that
bytes > 127 are written unchanged.

[emaste]

Please generate diffs with full context e.g. git diff -U99999 or git show -U99999 or use git arc. Change looks reasonable to me other than missing newline (noted by Phabricator). Probably should mention in the commit message that this is applying the approach from arm64.

[imp]

I think this looks good.

sys/conf/Makefile.arm

104

likely need a newline here.