Undefined references to EVP_rc4 on distros with OPENSSL_NO_RC4

[oskirby]

Over on the Mozilla VPN project, we have recently introduced some Rust components that make use of the OpenSSL package and this has been causing link issues on some of our users who are trying to build the client on Linux distributions without RC4 support.

Even though we aren't making use of RC4 anywhere in our codebase, we still encounter errors like this:

[ 92%] Linking CXX executable mozillavpn
/usr/bin/ld: ../vpnglean/x86_64-unknown-linux-gnu/debug/libvpnglean.a(openssl-473657804fb859a9.openssl.7f8ba334-cgu.5.rcgu.o): in function `openssl::symm::Cipher::rc4':
(REMOVED)/mozilla-vpn-client/build/cargo_home/registry/src/github.com-1ecc6299db9ec823/openssl-0.10.44/src/symm.rs:287: undefined reference to `EVP_rc4'
/usr/bin/ld: ../vpnglean/x86_64-unknown-linux-gnu/debug/libvpnglean.a(openssl-473657804fb859a9.openssl.7f8ba334-cgu.6.rcgu.o): in function `openssl::cipher::Cipher::rc4':
(REMOVED)/mozilla-vpn-client/build/cargo_home/registry/src/github.com-1ecc6299db9ec823/openssl-0.10.44/src/cipher.rs:328: undefined reference to `EVP_rc4'
collect2: error: ld returned 1 exit status
gmake[2]: *** [src/CMakeFiles/mozillavpn.dir/build.make:3977: src/mozillavpn] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:1120: src/CMakeFiles/mozillavpn.dir/all] Error 2
gmake: *** [Makefile:146: all] Error 2

I believe that we should check for the OPENSSL_NO_RC4 configuration when providing methods that use RC4.

This was reported by one of our users here: mozilla-mobile/mozilla-vpn-client#6228

[sfackler]

Ah yeah, that should require a patch like 62c8dfd