crater & clippy-service are non-functional due to lack of libsystemd

[codyps]

Possible solutions:

• extend clippy-service & crater to provide (via an environment variable) a location for required shared libs to be dropped, and switch back to a build script in rust-systemd.
  • relatively easy, and perfectly supports shared libs
  • we could adjust our travis scripts to do the same.
  • doesn't support the general issue of external deps, would also need to be able to drop other files (executables, data) somewhere in general.
• extend clippy-service & crater to allow projects to run pre-cargo-build scripts to install packages
  • matches the current situation with travis-ci
• extend cargo so that build scripts are provided with a location to store libraries (might require some LD_LIBRARY_PATH funny-ness in crater & clippy-service, or rpath control from build scripts).
  • probably the trickiest, but if done right would allow everything that uses cargo to magically get support for things that depend on shared libs.

[codyps]

• clippy-service no longer relevent (it's defunct)
• crater needs investigation