Allow building CLI with elixir 1.18.x

[VlkrS]

Tested with elixir 1.18.0-rc0, trivial change that should work without signing a CLA

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[pivotal-cla]

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[michaelklishin]

@pivotal-cla this is an obvious fix

[pivotal-cla]

@VlkrS This Pull Request contains an obvious fix. Signing the Contributor License Agreement is not necessary.

[michaelklishin]

@VlkrS thank you.