no_std-targeted build fails, getrandom dependency uses std

[alt3r-3go]

Hello everyone,
Looking at #22, I'd expect to be able to build the library for no_std target, but this currently failson getrandom like this:

$> cargo build --target thumbv7em-none-eabihf
   Compiling getrandom v0.2.3
   Compiling typenum v1.13.0
error[E0463]: can't find crate for `std`
 --> /home/user/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/getrandom-0.2.3/src/error_impls.rs:9:1
  |
9 | extern crate std;
  | ^^^^^^^^^^^^^^^^^ can't find crate
  |
  = note: the `thumbv7em-none-eabihf` target may not support the standard library

Is this expected to build at all, or things (e.g. your approach to supporting no_std) have changed since #22?

[robin-nitrokey]

As far as I understand, all dependencies that require std are behind the std feature (which is enabled by default). So compilation should work with cargo build --target thumbv7em-none-eabihf --no-default-features --features alloc. (alloc is required, see #51.)

[alt3r-3go]

Indeed, that was the reason, I apparently scanned the Cargo.toml too quickly and setting the features like that does compile fine. Thanks!