Error in package building : error[E0463]: can't find crate for `openssl_src`

["Hamzeh Nasajpour" <h.nasajpour@pantherx.org>]

Hi,

I face with an issue in one library that I'm packaging by myself. This library has one dependency to `rust-openssl@0.10.30`, I updated the `rust-openssl` to `0.10.30` and now I get this error in the package building:
```
...
patch-cargo-checksums: generate-checksums for guix-vendor/rust-zstd-sys-1.4.14+zstd.1.4.3.tar.gz
phase `patch-cargo-checksums' succeeded after 76.7 seconds
starting phase `build'                                                                                                                                                                                        
   Compiling autocfg v1.0.1
   Compiling memchr v2.3.3
   Compiling lazy_static v1.4.0
   Compiling libc v0.2.71
   Compiling regex-syntax v0.6.18
   Compiling pkg-config v0.3.17
   Compiling cc v1.0.58
   Compiling bitflags v1.2.1
   Compiling openssl v0.10.30
   Compiling foreign-types-shared v0.1.1
   Compiling cpython v0.3.0
   Compiling cfg-if v0.1.10
   Compiling thread_local v1.0.1
   Compiling foreign-types v0.3.2
   Compiling aho-corasick v0.7.13
   Compiling num-traits v0.2.12
   Compiling regex v1.3.9
   Compiling openssl-sys v0.9.58
error[E0463]: can't find crate for `openssl_src`
 --> /tmp/guix-build-python-etebase-py-0.30.0.drv-0/etebase-0.30.0/guix-vendor/rust-openssl-sys-0.9.58.tar.xz/build/main.rs:6:1
  |
6 | extern crate openssl_src;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

error: aborting due to previous error

For more information about this error, try `rustc --explain E0463`.
error: could not compile `openssl-sys`.
warning: build failed, waiting for other jobs to finish...
error: build failed
command "cargo" "build" "--features" "" "--release" failed with status 101
builder for `/gnu/store/5svg5z5s850j9s7wr6dmdh2kak9947hb-python-etebase-py-0.30.0.drv' failed with exit code 1

```

* I'm packaging the `etebase-py` : https://github.com/etesync/etebase-py/
* The `rust-openssl` dependency defined here: https://github.com/etesync/etebase-py/blob/master/Cargo.toml#L22
* I also packaged the `rust-openssl-src` and add it as dependency to my package definition but not resolved


Any idea? 



Regards,
Hamzeh