cryptol Docker image doesn't display git commit version properly

[RyanGlScott]

If you build cryptol from source and run --version on the resulting binary, it will tell you the git commit and branch information:

$ cabal -v0 run exe:cryptol -- --version
Cryptol 3.2.0.99
Git commit a172900c8fad75256f1fb3b8dfc6b7c62f1fd065
    branch master
FFI enabled

Unfortunately, doing the same thing in the Docker image does not produce any git-related information:

$ docker run --rm ghcr.io/galoisinc/cryptol:nightly --version
Cryptol 3.2.0.99
Git commit UNKNOWN
    branch UNKNOWN
FFI enabled

This is due to a silly oversight. The Docker image does not install git before compiling cryptol, and as a result, the build process is unable to embed the git commit/branch information into the cryptol binary.