Homebrew-core: ngspice seems to depend on fftw

[yunesj]

• [x] are reporting a bug others will be able to reproduce and not asking a question or requesting software. If you're not sure or want to ask a question do so on our Discourse: https://discourse.brew.sh. To get software added or changed in Homebrew please file a Pull Request
• [x] have a problem with brew install (or upgrade, reinstall) a single, Homebrew/homebrew-core formula (not cask) on macOS? If it's a general brew problem please file this issue at Homebrew/brew: https://github.com/Homebrew/brew/issues/new/choose. If it's a Linux problem please file this issue at https://github.com/Homebrew/linuxbrew-core/issues/new/choose. If it's a brew cask problem please file this issue at https://github.com/Homebrew/homebrew-cask/issues/new/choose. If it's a tap (e.g. Homebrew/homebrew-php) problem please file this issue at the tap.
• [x] ran brew update and can still reproduce the problem?
• [x] ran brew doctor, fixed all issues and can still reproduce the problem?
• [ ] ran brew gist-logs <formula> (where <formula> is the name of the formula that failed) and included the output link?
• [ ] if brew gist-logs didn't work: ran brew config and brew doctor and included their output with your issue?

$ brew install ngspice

$ ngspice
dyld: Library not loaded: /usr/local/opt/fftw/lib/libfftw3.3.dylib
  Referenced from: /usr/local/bin/ngspice
  Reason: image not found
Abort trap: 6

IIRC, installing fftw fixed the problem.

[issyl0]

Thanks for reporting this, @yunesj! I could reproduce this, so I've pushed a fix in the PR linked above.