Set _hart_stack_size = SIZEOF(.stack) for single-hart cores.

[janderholm]

I got the following error while building for a riscv core.

  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: rust-lld: error:
          ERROR(riscv-rt): .stack section is too small for allocating stacks for all the harts.
          Consider changing `_max_hart_id` or `_hart_stack_size`.

          rust-lld: error:
          ERROR(riscv-rt): .stack section is too small for allocating stacks for all the harts.
          Consider changing `_max_hart_id` or `_hart_stack_size`.

I can set _hart_stack_size to a smaller value, but I wonder if it would make more sense to set it to the size of the stack if the "single-hart" feature is enabled? They should effectively be the same anyway shouldn't they? This seem to work in my local memory.x:

_hart_stack_size = SIZEOF(.stack);

[janderholm]

Should the ASSERT be changed to >= as well? Or am I off?

ERROR(riscv-rt): .stack section is too small for allocating stacks for all the harts.
Consider changing `_max_hart_id` or `_hart_stack_size`.");

Currently if I set _hart_stack_size to 2048 and have a stack of 2048 this will result in a linking error.

[romancardenas]

Hi @janderholm ! Thanks for opening the issue!

I think your proposals are reasonable. Would you like to start a PR? Otherwise, I can try to implement your idea.

Note that _hart_stack_size = SIZEOF(.stack); must only be active when the single-hart feature is on. To do feature-dependent changes in the link.x, we use the build.rs script with ${FEATURE} wildcards.

[janderholm]

PR posted!

[romancardenas]

Closed as per #296