[BUG] Gem depends on the lastest version of Ruby (3.3.1) which breaks the installation via brew

[romanrev]

Describe the bug

doing gem seems to be dependent on a non-specified version of ruby which makes it pull the latest one, and from what I understand Ruby > 3.1 doesn't have any longer the exists? method, which breaks the installation.

To Reproduce

Just run the installation as described in the Wiki:

➤ brew gem install doing
==> Fetching dependencies for gem-doing: libyaml, ca-certificates, openssl@3 and ruby
==> Fetching libyaml
==> Downloading https://ghcr.io/v2/homebrew/core/libyaml/manifests/0.2.5
######################################################################### 100.0%
==> Downloading https://ghcr.io/v2/homebrew/core/libyaml/blobs/sha256:98c0cf81bc
######################################################################### 100.0%
==> Fetching ca-certificates
==> Downloading https://ghcr.io/v2/homebrew/core/ca-certificates/manifests/2024-
######################################################################### 100.0%
==> Downloading https://ghcr.io/v2/homebrew/core/ca-certificates/blobs/sha256:ca
######################################################################### 100.0%
==> Fetching openssl@3
==> Downloading https://ghcr.io/v2/homebrew/core/openssl/3/manifests/3.3.0-1
######################################################################### 100.0%
==> Downloading https://ghcr.io/v2/homebrew/core/openssl/3/blobs/sha256:ec6f9daf
######################################################################### 100.0%
==> Fetching ruby
==> Downloading https://ghcr.io/v2/homebrew/core/ruby/manifests/3.3.1
######################################################################### 100.0%
==> Downloading https://ghcr.io/v2/homebrew/core/ruby/blobs/sha256:737689c80a9c9
######################################################################### 100.0%
==> Fetching gem-doing
==> Fetching doing from gem source
Fetching doing-2.1.86.gem
Downloaded doing-2.1.86
Warning: Cannot verify integrity of 'doing-2.1.86.gem'.
No checksum was provided.
For your reference, the checksum is:
  sha256 "0e4873e94625bdcdc438657a04c34f66757753bce0a49f19b7bb6a49282d88c0"
==> Installing dependencies for gem-doing: libyaml, ca-certificates, openssl@3 and ruby
==> Installing gem-doing dependency: libyaml
==> Downloading https://ghcr.io/v2/homebrew/core/libyaml/manifests/0.2.5
Already downloaded: /Users/<user>/Library/Caches/Homebrew/downloads/5f6b0af1730aa1bc02f8021c90ed7ffe988eeba95eec83e6c828f77332ba6406--libyaml-0.2.5.bottle_manifest.json
==> Pouring libyaml--0.2.5.arm64_sonoma.bottle.tar.gz
🍺  /opt/homebrew/Cellar/libyaml/0.2.5: 11 files, 354.9KB
==> Installing gem-doing dependency: ca-certificates
==> Downloading https://ghcr.io/v2/homebrew/core/ca-certificates/manifests/2024-
Already downloaded: /Users/<user>/Library/Caches/Homebrew/downloads/c431e0186df2ccc2ea942b34a3c26c2cebebec8e07ad6abdae48447a52c5f506--ca-certificates-2024-03-11.bottle_manifest.json
==> Pouring ca-certificates--2024-03-11.all.bottle.tar.gz
==> Regenerating CA certificate bundle from keychain, this may take a while...
🍺  /opt/homebrew/Cellar/ca-certificates/2024-03-11: 4 files, 232.3KB
==> Installing gem-doing dependency: openssl@3
==> Downloading https://ghcr.io/v2/homebrew/core/openssl/3/manifests/3.3.0-1
Already downloaded: /Users/<user>/Library/Caches/Homebrew/downloads/cd7e4cb72da375d51619d8c60fb91a70696e352edb515631b5751d05342e471d--openssl@3-3.3.0-1.bottle_manifest.json
==> Pouring [email protected]_sonoma.bottle.1.tar.gz
🍺  /opt/homebrew/Cellar/openssl@3/3.3.0: 6,977 files, 32.4MB
==> Installing gem-doing dependency: ruby
==> Downloading https://ghcr.io/v2/homebrew/core/ruby/manifests/3.3.1
Already downloaded: /Users/<user>/Library/Caches/Homebrew/downloads/844452a66e10bb7cb2dcc8942491cf29cf39ee3e4f47e379bd22f1ff461e30e4--ruby-3.3.1.bottle_manifest.json
==> Pouring ruby--3.3.1.arm64_sonoma.bottle.tar.gz
🍺  /opt/homebrew/Cellar/ruby/3.3.1: 19,716 files, 51.4MB
==> Installing gem-doing
Error: An exception occurred within a child process:
  NoMethodError: undefined method `exists?' for class File

Expected behavior

Gem doing should be installed without any errors

Desktop (please complete the following information):

• Platform: Mac
• OS: Sonoma
• Version 14.3

Doing version

• Result of doing -v

Ruby version

• Result of ruby -v

Additional context

Add any other context about the problem here.