[CI] Add aarch64 build jobs

[cyring]

Thanks a lot.

According to this issue, we can remove old Alpine/musl from the CoreFreq support

EDIT: for same Alpine musl limitations reasons, random_data is missing but that structure is a CoreFreq prerequisite.

Missing qsort_r is the last issue to solve with musl libc

[cyring]

For registers without architectural names, or simply unsupported by GAS

read_sysreg_s within asm/sysreg.h had appeared in kernel v5.5. This is a sophisticated function I have not planed to rewrite for older kernels.

Thus, if possible, I suggest we mute those CI builds:

• ubuntu-16.04-xenial aarch64
• ubuntu-14.04-trusty aarch64

EDIT: Issue fixed