* gnu/packages/crates-io.scm (rust-backtrace-0.3): Update to 0.3.66.
[arguments]: Replace rust-addr2line-0.14 with rust-addr2line-0.17,
rust-miniz-oxide-0.4 with rust-miniz-oxide-0.5, and rust-object-0.23 with
rust-object-0.29; add rust-libloading-0.7 and rust-cc-1; remove
rust-backtrace-sys-0.1.