Problems with asciidoctor gem after ruby update

[Daniel Abrahamsson <daniel.abrahamsson@prover.com>]

Hi,

I’m not sure if the issue is cygwin-specific or not, but I do not have a linux box with a sufficiently new version of ruby to test with. The errors started showing up after the recent updates of the ruby and rubygems packages.

When installing asciidoctor via `gem install asciidoctor`, a asciidoctor "binary" is placed in "$HOME/bin". However, when running `asciidoctor` I get:

```
$ asciidoctor
/home/daab/bin/asciidoctor: line 6: /home/daab/bin/ruby: No such file or directory
```

The asciidoctor binary is looking for ruby in the wrong place (it should be looking for the system ruby).

Version output:
```
$ asciidoctor -v
Asciidoctor 2.0.18 [https://asciidoctor.org]
Runtime Environment (ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-cygwin]) (lc:UTF-8 fs:UTF-8 in:UTF-8 ex:UTF-8)
$ ruby -v
ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-cygwin]
$ gem -v
3.4.12
```

The asciidcoctor binary on the upgraded system starts with these lines:

```
#!/bin/sh
# -*- ruby -*-
_=_\
=begin
bindir="${0%/*}"
exec "$bindir/ruby" "-x" "$0" "$@"
=end
#!/usr/bin/ruby.exe
#
# This file was generated by RubyGems.
```

On a non-upgraded system, we instead have:

```
#!/usr/bin/ruby.exe
#
# This file was generated by RubyGems.
#
# The application 'asciidoctor' is installed as part of a gem, and
# this file is here to facilitate running it.
#
```
require 'rubygems'

// Daniel