Redirect stderr to stdout via -1; Unbreak dk 9 test

[kazarmy]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository
• I made sure to follow the project's coding style
• I've documented or updated the documentation of every function and struct this PR changes. If not so I've explained why.
• I've added tests that prove my fix is effective or that my feature works (if possible)
• I've updated the rizin book with the relevant information (if needed)

Detailed description

This pr adds a -1 flag to Rizin to redirect stderr to stdout, so that the dk 9 test can be unbroken.

Test plan

The addition is appropriate. All builds are green.

Closing issues

...

[wargio]

i'm ok with this, but the PR should be renamed to Fix sig 9 on child and introduce stderr redirection via -1 (or similar)

[kazarmy]

Ok