support for illumos systems

[jclulow]

At the moment, when building for an illumos system, you get this error:

error: failed to run custom build command for `openssl-sys v0.9.53`

Caused by:
  process didn't exit successfully: `/rust/build/x86_64-unknown-linux-gnu/stage1-tools/release/build/openssl-sys-cd2ff60dc414d5d9/build-script-main` (exit code: 101)
--- stdout
cargo:rustc-cfg=const_fn

--- stderr
thread 'main' panicked at 'don't know how to configure OpenSSL for x86_64-sun-solaris', /root/.cargo/registry/src/github.com-1ecc6299db9ec823/openssl-src-111.6.1+1.1.1d/src/lib.rs:180:18
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

The fix is pretty simple:

diff --git a/src/lib.rs b/src/lib.rs
index 12e3438..3a177ad 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -180,6 +180,7 @@ impl Build {
             "x86_64-unknown-linux-gnu" => "linux-x86_64",
             "x86_64-unknown-linux-musl" => "linux-x86_64",
             "x86_64-unknown-netbsd" => "BSD-x86_64",
+            "x86_64-sun-solaris" => "solaris64-x86_64-gcc",
             "wasm32-unknown-emscripten" => "gcc",
             "wasm32-unknown-unknown" => "gcc",
             "aarch64-apple-ios" => "ios64-cross",

I hit this as part of getting illumos/Solaris support into rustup. Is it alright if I open a PR with the change above? With the above patched in, everything works and I'm able to get a static vendored OpenSSL in my rustup binary.

Additionally, it looks like for openssl-sys to pick such a change up, we'd also need to update the version and publish the crate? Is it OK if I include bumping the version to 111.6.2+1.1.1d in the PR, or do you want to do that separately?

Thanks!

[alexcrichton]

A PR shouuld be good to add support here, and a new release can then be made!