sync.stdatomic: add atomic_thread_fence(), cpu_relax()

[kbkpbot]

Add atomic_thread_fence() support.
Add cpu_relax() to support building low cpu-usage spin lock.

[huly-for-github]

Connected to Huly®: V_0.6-23046

[spytheman]

@tankf33der, can you please check if v test vlib/sync will pass on riscv64, with this PR?

[kbkpbot]

@tankf33der, can you please check if v test vlib/sync will pass on riscv64, with this PR?

I have no riscv64, so it need someone else help here. :)
BTW, I submit a new commit and try to support other platforms. (not tested yet)

[tankf33der]

@tankf33der, can you please check if v test vlib/sync will pass on riscv64, with this PR?

latest v on ubuntu 24.10 successfully passed vlib/sync on master and on this PR.

[tankf33der]

@tankf33der, can you please check if v test vlib/sync will pass on riscv64, with this PR?

I have no riscv64, so it need someone else help here. :) BTW, I submit a new commit and try to support other platforms. (not tested yet)

I can provide all the information on how to set up qemu+riscv64.
Just find me on Discord.

[spytheman]

@kbkpbot, @tankf33der, thank you, for making V better.

[kbkpbot]

@tankf33der, can you please check if v test vlib/sync will pass on riscv64, with this PR?

I have no riscv64, so it need someone else help here. :) BTW, I submit a new commit and try to support other platforms. (not tested yet)

I can provide all the information on how to set up qemu+riscv64. Just find me on Discord.

Thank for information.
I just install qemu + riscv :)