Building with esp-id-sys/std fails on nightly in linux due to missing O_NOFOLLOW

[eteq]

Bug description

When I start a new project based on the RISCV/nightly rust toolchain, I get an error about a missing symbol from libc in the build of std (exact message below). I think the origin of this is rust-lang/rust@9c46cdb, which introduced the use of O_NOFOLLOW in std. A workaround that fixes it is to use nightly-2025-08-19 as the toolchain, which is the last one before the offending commit was merged.

The catch is: I don't really understand why this is failing, which is why I'm reporting it here instead of upstream. It still might be an upstream bug of course, but if I make a non-esp-idf-sys-based project everything works fine even on the latest nightly. That said, I really don't understand the std-building process well enough to know for sure how widespread this problem. Happy to try some more troubleshooting if someone offers guidance, though.

exact error message

error[E0425]: cannot find value `O_NOFOLLOW` in crate `libc`
   --> /home/esp/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/fs/mod.rs:122:43
    |
122 |     OpenOptions::new().custom_flags(libc::O_NOFOLLOW).open(path)?.set_permissions(perm)
    |                                           ^^^^^^^^^^ not found in `libc`

For more information about this error, try `rustc --explain E0425`.

• Would you like to work on a fix? maybe

To Reproduce

1. use the esp-idf-template to make a esp-idf-sys/std-based esp crate
2. set everything up following the default instructions in the rust on esp book (I used the devcontainer, but I got identical results on a system set up similarly)
3. run cargo check

Expected behavior

The build should succeed

Environment

• Crate (esp-idf-sys) version: master
• ESP-IDF branch or tag: 5.3
• Target device (MCU): esp32c6 or probably anything RISCV that uses nightly
• OS: nixos

[Vollbrecht]

This is a upstream compiler problem, and there is already a PR addressing the issue here