Fix and install bash completion for cbmc

[tautschnig]

1. Use a pragma-free (and working) approach to extract CBMC_OPTIONS.
2. Add completion of all completable arguments to command-line options.
3. Make CMake's install target install the resulting bash completion
   script in etc/bash_completion.d
4. Make the .deb package depend on bash-completion for the now-included
   completion snippet to be useful.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

Merging #6776 (49d11dc) into develop (13d0c18) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #6776   +/-   ##
========================================
  Coverage    77.76%   77.76%           
========================================
  Files         1568     1568           
  Lines       180318   180318           
========================================
  Hits        140231   140231           
  Misses       40087    40087           

Impacted Files	Coverage Δ
src/goto-cc/gcc_cmdline.cpp	79.23% <ø> (ø)
src/goto-cc/gcc_mode.cpp	68.47% <100.00%> (ø)

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[tautschnig]

Requires #6775 for CI to pass.

[NlightNFotis]

I see this has some handling of MacOS as an os - but osX uses zsh. Can that reuse that configuration or not?

(sorry, I'm in a meeting now so I can't play around extensively with this, but will have a play with this later.)

[NlightNFotis]

Okay I did play around with this a bit, and it looks good (works fine locally).

@tautschnig Could you please also update the documentation the Readme.md, at the zsh part to include:

autoload -Uz compinit
compinit

on the top of the .zshrc? That is needed unless someone is running Oh my ZSH. The source for this is https://unix.stackexchange.com/questions/339954/zsh-command-not-found-compinstall-compinit-compdef

[NlightNFotis]

This folder doesn't exist in osX, at least not by default. Is this the correct one for that platform?

[tautschnig]

This may require playing with the brew configuration. I have /usr/local/etc/bash_completion.d/ as created by homebrew, but I'm not sure this will work just like this, or whether we need to adjust the homebrew formula.

[NlightNFotis]

I have no idea what's up with the duplicate comments, please ignore them (I didn't create them, so I'm kind of scared to delete them in case it deletes the originals as well)

[tautschnig]

Okay I did play around with this a bit, and it looks good (works fine locally).

@tautschnig Could you please also update the documentation the Readme.md, at the zsh part to include:

autoload -Uz compinit
compinit

on the top of the .zshrc? That is needed unless someone is running Oh my ZSH. The source for this is https://unix.stackexchange.com/questions/339954/zsh-command-not-found-compinstall-compinit-compdef

@NlightNFotis My apologies for taking this long to get back to you (and this PR)! I have now updated the instructions, could you please (whenever time permits) take a look whether the new documentation matches your expectations?

[NlightNFotis]

LGTM, thanks for the comments with the explanation!