riscv/riscv_addrenv.c: Allocate heap for default task stacksize

[pussuw]

Summary

1 page might not be enough, if the task has a bigger stack. Best effort is to allocate the default amount, however this won't work will all tasks either. See issue #5811 for more details.

Impact

Fixes system crash when not enough heap is allocated for new task's stack. Only affects builds with CONFIG_BUILD_KERNEL.

Testing

Target with processes whose stack size is > 1 page (4K)

[pussuw]

The risc-v CI seems to be broken, it cannot find the toolchain. Is this a known issue ?

    command: riscv64-unknown-elf-gcc -MT ./task_create.o  -M '-fno-common' '-Wall' '-Wstrict-prototypes' '-Wshadow' '-Wundef' '-Wno-attributes' '-Wno-unknown-pragmas' '-Wno-psabi' '-Os' '-fno-strict-aliasing' '-fomit-frame-pointer' '-ffunction-sections' '-fdata-sections' '-g' '-march=rv64imafdc' '-mabi=lp64d' '-mcmodel=medany' '-isystem' '/github/workspace/sources/nuttx/include' '-D__NuttX__' '-D__KERNEL__' '-Wno-cpp' '-Werror' '-pipe' '-I' '/github/workspace/sources/nuttx/sched' ./task/task_create.c

make[2]: *** [/github/workspace/sources/nuttx/tools/Config.mk:228: task_create.ddc] Error 1
sh: 1: riscv64-unknown-elf-gcc: not found
ERROR: riscv64-unknown-elf-gcc failed: 127

[xiaoxiang781216]

Yes, I am looking the problem due to toolchain upgrade to 13.0.2 by #10306.

[xiaoxiang781216]

Let's ignore riscv ci temp fail and merge this simple change directly.