riscv32imac-unknown-none-elf support

[flippette]

Hi,

I'm trying to get rustls to work on a bare-metal project using the riscv32imac-unknown-none-elf target.

Here's the relevant section of my Cargo.toml:

[dependencies.getrandom]
version = "0.2"
features = ["custom"]

[dependencies.ring]
git = "https://github.com/briansmith/ring"
rev = "b939c18e27554fdfcbf8d998932dbc4ddd479c54"
features = ["less-safe-getrandom-custom-or-rdrand"]

[dependencies.rustls]
version = "0.23"
default-features = false
features = ["ring"]

I have provided a custom getrandom implementation via register_custom_getrandom!.

I'm getting this build error:

warning: [email protected]: Inherited flag "-fno-omit-frame-pointer" is not supported by the currently used CC
warning: [email protected]: Inherited flag "-fno-omit-frame-pointer" is not supported by the currently used CC
warning: [email protected]: In file included from /home/flippette/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ring-0.17.9/include/ring-core/base.h:74,
warning: [email protected]:                  from /home/flippette/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ring-0.17.9/include/ring-core/mem.h:60,
warning: [email protected]:                  from /home/flippette/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ring-0.17.9/crypto/curve25519/curve25519.c:22:
warning: [email protected]: /home/flippette/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ring-0.17.9/include/ring-core/target.h:53:2: error: #error "Unknown target CPU"
warning: [email protected]:    53 | #error "Unknown target CPU"
warning: [email protected]:       |  ^~~~~
warning: [email protected]: In file included from /home/flippette/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ring-0.17.9/crypto/curve25519/internal.h:20,
warning: [email protected]:                  from /home/flippette/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ring-0.17.9/crypto/curve25519/curve25519.c:24:
warning: [email protected]: /home/flippette/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ring-0.17.9/crypto/curve25519/../internal.h:246:2: error: #error "Must define either OPENSSL_32_BIT or OPENSSL_64_BIT"
warning: [email protected]:   246 | #error "Must define either OPENSSL_32_BIT or OPENSSL_64_BIT"

I've tried setting TARGET_CC='riscv32-unknown-elf-gcc' to no avail.