Cross compilation results in size mismatch of `ssize_t` and pointer size

[aparcar]

I'm trying to build project for multiple architectures but it fails on aarch64 due to a mismatch of the ssize_t and the pointer size. Full error message below. I see that it's possible to set --no-size_t-is-usize but wonder if that's the correct way to do so, I see that ops-sys explicitly sets this option to true in build.rs.

error: failed to run custom build command for oqs-sys v0.9.1+liboqs-0.9.0 (https://github.com/open-quantum-safe/liboqs-rust.git?rev=07e569027cf4dcaa5991cf2f16d63b0363957327#07e56902)

Caused by:
  process didn't exit successfully: `/home/aparcar/openwrt/build_dir/target-aarch64_generic_musl/rosenpass-72f68c9bac3b1b3cd09110493f9b953f6dc29eff/target/release/build/oqs-sys-80409713af391698/build-script-build` (exit status: 101)
  --- stdout
  cargo:rerun-if-env-changed=LIBOQS_NO_VENDOR
  cargo:rerun-if-env-changed=LIBOQS_NO_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS_aarch64-unknown-linux-musl
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS_aarch64_unknown_linux_musl
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_ALLOW_CROSS
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS
  cargo:rerun-if-env-changed=PKG_CONFIG_aarch64-unknown-linux-musl
  cargo:rerun-if-env-changed=PKG_CONFIG_aarch64_unknown_linux_musl
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG_aarch64-unknown-linux-musl
  cargo:rerun-if-env-changed=PKG_CONFIG_aarch64_unknown_linux_musl
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG
  cargo:rerun-if-env-changed=LIBOQS_STATIC
  cargo:rerun-if-env-changed=LIBOQS_DYNAMIC
  cargo:rerun-if-env-changed=PKG_CONFIG_ALL_STATIC
  cargo:rerun-if-env-changed=PKG_CONFIG_ALL_DYNAMIC
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH_aarch64-unknown-linux-musl
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH_aarch64_unknown_linux_musl
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_PATH
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR_aarch64-unknown-linux-musl
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR_aarch64_unknown_linux_musl
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_LIBDIR
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_aarch64-unknown-linux-musl
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_aarch64_unknown_linux_musl
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_SYSROOT_DIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR
  cargo:rerun-if-env-changed=SYSROOT
  cargo:rerun-if-env-changed=LIBOQS_STATIC
  cargo:rerun-if-env-changed=LIBOQS_DYNAMIC
  cargo:rerun-if-env-changed=PKG_CONFIG_ALL_STATIC
  cargo:rerun-if-env-changed=PKG_CONFIG_ALL_DYNAMIC
  cargo:rustc-link-search=native=/home/aparcar/openwrt/staging_dir/target-aarch64_generic_musl/usr/lib
  cargo:rustc-link-lib=oqs
  cargo:rerun-if-env-changed=PKG_CONFIG_aarch64-unknown-linux-musl
  cargo:rerun-if-env-changed=PKG_CONFIG_aarch64_unknown_linux_musl
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG
  cargo:rerun-if-env-changed=LIBOQS_STATIC
  cargo:rerun-if-env-changed=LIBOQS_DYNAMIC
  cargo:rerun-if-env-changed=PKG_CONFIG_ALL_STATIC
  cargo:rerun-if-env-changed=PKG_CONFIG_ALL_DYNAMIC
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH_aarch64-unknown-linux-musl
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH_aarch64_unknown_linux_musl
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_PATH
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR_aarch64-unknown-linux-musl
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR_aarch64_unknown_linux_musl
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_LIBDIR
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_aarch64-unknown-linux-musl
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_aarch64_unknown_linux_musl
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_SYSROOT_DIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR

  --- stderr
  thread 'main' panicked at /home/aparcar/openwrt/dl/cargo/registry/src/index.crates.io-6f17d22bba15001f/bindgen-0.69.4/codegen/mod.rs:912:25:
  assertion `left == right` failed: Target platform requires `--no-size_t-is-usize`. The size of `ssize_t` (4) does not match the target pointer size (8)
    left: 4
   right: 8
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace