[GSoC] Procedure for linker script of new port

[Amaan Cheval]

Hi!

We discussed this briefly in a thread earlier[1], but I'd like more
definitive advice if possible. What are the things to keep in mind
when designing the linker script for a new port? As far as I can tell,
I can just use the default one (as shown by "x86_64-rtems5-ld
--verbose") with a few modifications to:

- Try to offload the things bsp_specs does into the linker script, as
Joel requested[2].
- Add configuration parameters if required (I see this on other
architectures, for eg. bsp_stack_irq_size on
./*/arm/shared/startup/linkcmds.base).

Is there anything else to keep in mind? I believe not, but I figured
I'd confirm.

[1] https://lists.rtems.org/pipermail/devel/2018-April/021050.html
[2] https://lists.rtems.org/pipermail/devel/2018-May/021430.html