AArch64 scheduler performs worse when optimized

[mkroening]

hermit-c's pthreads.c test performs considerably worse when kernel optimizations are enabled. Suddenly, we have a huge number of rescheduling interrupts. This should be possible to reproduce in Rust.

$ cargo xtask ci c --arch aarch64 --target pthreads --smp 4 qemu
...
../src/pthreads.c:44: assert(count_value == parallelism * ITERATIONS) successful
[   36.035796][0][INFO  interrupts] Number of interrupts
[   36.039786][0][INFO  interrupts] [0][Reschedule]: 5
[   36.040927][0][INFO  interrupts] [1][Reschedule]: 3
[   36.041966][0][INFO  interrupts] [2][Reschedule]: 3
[   36.042901][0][INFO  interrupts] [3][Reschedule]: 3

40e0c6e (a year ago):

$ cargo xtask ci c --arch aarch64 --buildtype release --target pthreads --smp 4 qemu
...
../src/pthreads.c:47: assert(count_value == parallelism * ITERATIONS) successful
[   41.790805][0][INFO] Number of interrupts
[   37.063989][0][INFO] [0][Reschedule]: 101420
[   37.064255][0][INFO] [1][Reschedule]: 165798
[   37.064444][0][INFO] [2][Reschedule]: 164730
[   37.064600][0][INFO] [3][Reschedule]: 110663

5312fca (current main):

$ cargo xtask ci c --arch aarch64 --buildtype release --target pthreads --smp 4 qemu
...
../src/pthreads.c:44: assert(count_value == parallelism * ITERATIONS) successful
[   47.009291][0][INFO  interrupts] Number of interrupts
[   43.805069][0][INFO  interrupts] [0][Reschedule]: 349560
[   43.805359][0][INFO  interrupts] [1][Reschedule]: 632670
[   43.805540][0][INFO  interrupts] [2][Reschedule]: 326619
[   43.805706][0][INFO  interrupts] [3][Reschedule]: 671266

A workaround for this worsening of performance in the last year is added in:

• build(deps): update kernel submodule hermit-c#48

[mkroening]

This is also the reason for the Laplace timeouts on ARM.