Add chacha-sys crate (#4620)

* af9ff9c7f9/src/cpu-crypt

* Add chacha-sys crate

* Remove chacha feature

* Remove erasure feature

* Add .gitignore

chacha-sys/build.rs

@@ -0,0 +1,8 @@
+extern crate cc;
+
+fn main() {
+    cc::Build::new()
+        .file("cpu-crypt/chacha20_core.c")
+        .file("cpu-crypt/chacha_cbc.c")
+        .compile("libcpu-crypt");
+}