gh-112779: Check 1-byte atomics in configure

[colesbury]

This fixes RISC-V compilation for GCC versions earlier than GCC 13.

GCC versions 12 and earlier require libatomic library support for 1-byte and 2-byte atomics on RISC-V, but not for 8-byte atomics. The configure script only checked 8-byte atomics and so did not think that -latomic was necessary.

GCC 13 already worked. It does not require libatomic support for any of the sizes we use (1, 2, 4, or 8 bytes).

• Issue: Build Error on RISC-V: undefined reference to `__atomic_exchange_1' #112779

[colesbury]

See https://gcc.godbolt.org/z/rPbrns6P8:

_Py_atomic_add_int8:
        addi    sp,sp,-16
        li      a2,5
        andi    a1,a1,0xff
        sd      ra,8(sp)
        call    __atomic_fetch_add_1
        ld      ra,8(sp)
        slliw   a0,a0,24
        sraiw   a0,a0,24
        addi    sp,sp,16
        jr      ra

_Py_atomic_add_int64:
        mv      a5,a0
        fence iorw,ow; amoadd.d.aq a0,a1,0(a5)
        ret

[corona10]

I will take a look at this weekend

[erlend-aasland]

Looks good to me.

[corona10]

Overall, it looks good to me.
But would you like to leave a comment why 1-byte atomic checking and 8-byte atomic is checking is needed with compiler version issue?

In the future, we need to know why the check-ing was needed but without comment, it could be easily forgotten.

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