There are a variety of additional scripts that are included with the
JRuby installation that use JRuby itself.
For instance the `bin/gem` had the following contents:
```bash
❯ cat /nix/store/kglkqf56ii83yl6yrgcaj5r3s9m2fzr0-jruby-9.2.13.0/bin/gem
load File.join(File.dirname(__FILE__), 'jgem')
```
This is clearly wrong. Patchshebangs was not picking up the fix as part
of stdenv because the patch is not a build input but the final output
itself.
We have to rely on substituteInPlace so that we get the correct version.
```bash
❯ cat /nix/store/k4fnrn0dcsh2wzw81217r0ywsspb468f-jruby-9.2.13.0/bin/gem
```
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