Compatibility to special folder names

[fionera]

When running Colmena from a folder containing an @ sign, it will crash.

[INFO ] Using configuration: /home/tim/src/internal/infra@2/hive.nix
[INFO ] Enumerating nodes...
error: syntax error, unexpected '@', expecting ';'

       at «string»:1:140:

            1| with builtins; let eval = import /run/user/1000/colmena-assets-mFbYbX/eval.nix; hive = eval { rawHive = import /home/tim/src/internal/infra@
             |                                                                                                                                            ^
[ERROR] -----
[ERROR] Operation failed with error: Child process exited with error code: 1
Backtrace:
   0: <backtrace::capture::Backtrace as snafu::GenerateImplicitData>::generate
   1: <tokio::process::Command as colmena::util::CommandExt>::capture_output::{{closure}}
   2: <tokio::process::Command as colmena::util::CommandExt>::capture_json::{{closure}}
   3: colmena::nix::hive::Hive::select_nodes::{{closure}}
   4: colmena::troubleshooter::run_wrapped::{{closure}}
   5: colmena::cli::run::{{closure}}
   6: tokio::runtime::park::CachedParkThread::block_on
   7: tokio::runtime::scheduler::multi_thread::MultiThread::block_on
   8: tokio::runtime::runtime::Runtime::block_on
   9: std::panicking::try
  10: colmena::main
  11: std::sys_common::backtrace::__rust_begin_short_backtrace
  12: std::rt::lang_start::{{closure}}
  13: std::rt::lang_start_internal
  14: main
  15: __libc_start_call_main
  16: __libc_start_main@@GLIBC_2.34
  17: _start