release fails to build in ubuntu 18.04.1 in WSL

[kyhwana]

Trying to build via "cargo build --release" on the master branch (downloaded via fails with the following errors:
Compiling ctrlc v3.1.1
error[E0658]: non-reference pattern used to match a reference (see issue #42640)
--> /home/kyhwana/.cargo/registry/src/github.com-1ecc6299db9ec823/ring-0.13.2/build.rs:375:9
|
375 | let (_, _, perlasm_format) = ASM_TARGETS.iter().find(|entry| {
| ^^^^^^^^^^^^^^^^^^^^^^ help: consider using a reference: &(_, _, perlasm_format)

error[E0658]: non-reference pattern used to match a reference (see issue #42640)
--> /home/kyhwana/.cargo/registry/src/github.com-1ecc6299db9ec823/ring-0.13.2/build.rs:674:9
|
674 | for (src, dst) in src_dst {
| ^^^^^^^^^^ help: consider using a reference: &(src, dst)

error[E0658]: non-reference pattern used to match a reference (see issue #42640)
--> /home/kyhwana/.cargo/registry/src/github.com-1ecc6299db9ec823/ring-0.13.2/build.rs:737:35
|
737 | RING_SRCS.iter().any(|(_, f)| cmp(f)) ||
| ^^^^^^ help: consider using a reference: &(_, f)

error[E0658]: non-reference pattern used to match a reference (see issue #42640)
--> /home/kyhwana/.cargo/registry/src/github.com-1ecc6299db9ec823/ring-0.13.2/build.rs:741:35
|
741 | RING_SRCS.iter().any(|(_, f)| cmp(f)) ||
| ^^^^^^ help: consider using a reference: &(_, f)

error: aborting due to 4 previous errors

error: Could not compile ring.
warning: build failed, waiting for other jobs to finish...
error: build failed

cargo --version
cargo 0.26.0
rustc --version
rustc 1.25.0

[int08h]

Hello @kyhwana, Roughenough uses ring v0.13.x for cryptographic operations. According to ring's documentation it guarantees compatibility only with the latest Stable Rust (which is currently 1.29).

The version Ubuntu 18.04.1 provides (given the output of rustc --version you reported) is 1.25 which seems to be too old to compile Ring.

I'll update the docs to reflect this requirement.