Adds an extra '-' to an instruction

[martinomburajr]

This instruction does not work cargo objdump --bin app -- -d -no-show-raw-insn

Instead I had to add an extra '-' at the start of -no-show-raw-insn

rustc 1.58.0-nightly

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @adamgreig (or someone else) soon.

Please see the contribution instructions for more information.

[bors[bot]]

Build succeeded:

• build (1.58.1)
• build (stable)