Use `x86` instead of `i386` when compiling for i586- and i686- Rust targets on Linux

[link2xt]

New Zig versions use x86 instead of i386 as an architecture name: https://github.com/ziglang/zig/pull/13101

For Windows there is already a check for new Zig: https://github.com/rust-cross/cargo-zigbuild/blob/f2c70a102908aabfe7256fad3533a3701839acbe/src/zig.rs#L735-L738 It was introduced in https://github.com/rust-cross/cargo-zigbuild/pull/110

For Linux cargo-zigbuild still uses "i386" unconditionally: https://github.com/rust-cross/cargo-zigbuild/blob/f2c70a102908aabfe7256fad3533a3701839acbe/src/zig.rs#L713-L714

I am filing the issue so it is easier to find the reason for those who try to compile for i686 on Linux using nightly Zig builds. There is however no need to fix this now as I plan to switch from cargo-zigbuild to my own simple wrapper here: https://github.com/deltachat/deltachat-core-rust/pull/4243 Maybe it is easier to wait until Zig 0.11 release and switch to using x86 unconditionally or at least wait for someone requesting this bug to be fixed in the comment to this issue.

[messense]

That change was reverted in https://github.com/ziglang/zig/pull/13460?

[link2xt]

That change was reverted in ziglang/zig#13460?

No, it does not fully revert the change. I think this is why it says "not arch" in the title. The output of zig targets for me looks like this:

{
 "arch": [
  "arm",
  "armeb",
  "aarch64",
  "aarch64_be",
  "aarch64_32",
  "arc",
  "avr",
  "bpfel",
  "bpfeb",
  "csky",
  "dxil",
  "hexagon",
  "loongarch32",
  "loongarch64",
  "m68k",
  "mips",
  "mipsel",
  "mips64",
  "mips64el",
  "msp430",
  "powerpc",
  "powerpcle",
  "powerpc64",
  "powerpc64le",
  "r600",
  "amdgcn",
  "riscv32",
  "riscv64",
  "sparc",
  "sparc64",
  "sparcel",
  "s390x",
  "tce",
  "tcele",
  "thumb",
  "thumbeb",
  "x86",
  "x86_64",
  "xcore",
  "nvptx",
  "nvptx64",
  "le32",
  "le64",
  "amdil",
  "amdil64",
  "hsail",
  "hsail64",
  "spir",
  "spir64",
  "spirv32",
  "spirv64",
  "kalimba",
  "shave",
  "lanai",
  "wasm32",
  "wasm64",
  "renderscript32",
  "renderscript64",
  "ve",
  "spu_2"
 ],
 "os": [
...

There is no i386 architecture, the architecture (first word in the target triple) is named x86 now, but it was named i386 in zig 0.10.

[link2xt]

In cpus section there are many CPUs defined, including:

   "i386": [
    "slow_unaligned_mem_16",
    "vzeroupper",
    "x87"
   ],
   "i486": [
    "slow_unaligned_mem_16",
    "vzeroupper",
    "x87"
   ],
   "i586": [
    "cx8",
    "slow_unaligned_mem_16",
    "vzeroupper",
    "x87"
   ],
   "i686": [
    "cmov",
    "cx8",
    "slow_unaligned_mem_16",
    "vzeroupper",
    "x87"
   ],

This is what goes into -mcpu flag as far as I understand.