Slic3r cask does not provide slic3r CLI tools

[jasonhemann]

Verification

• [X] I understand that if I ignore these instructions, my issue may be closed without review.
• [X] I have retried my command with --force.
• [X] I ran brew update-reset && brew update and retried my command.
• [X] I ran brew doctor, fixed as many issues as possible and retried my command.
• [X] I have checked the instructions for reporting bugs.
• [X] I made doubly sure this is not a checksum does not match / SHA256 mismatch error (do not open an issue before trying to open a PR to fix first).

Description of issue

Bug/Feature request. Slic3r has a nice CLI interface. However, even after a successful installation, I do not see where the slic3r binary is installed.

is that correct?

Command that failed

brew install slic3r && slic3r

Output of command with --verbose --debug

brew install slic3r --verbose --debug 
/opt/homebrew/Library/Homebrew/brew.rb (Cask::CaskLoader::FromAPILoader): loading slic3r
Warning: Not upgrading slic3r, the latest version is already installed

Output of brew doctor and brew config

I bet this isn't relevant, but 

brew doctor && brew config
Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry or file an issue; just ignore this. Thanks!

Warning: Some installed formulae are deprecated or disabled.
You should find replacements for the following formulae:
  arangodb
  exa
  ghc@8.10
  idris
  lean
  mono
  openssl@1.1

Warning: Unbrewed dylibs were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected dylibs:
  /usr/local/lib/libprofiler.0.dylib
  /usr/local/lib/libtcmalloc.4.dylib
  /usr/local/lib/libtcmalloc_and_profiler.4.dylib
  /usr/local/lib/libtcmalloc_debug.4.dylib
  /usr/local/lib/libtcmalloc_minimal.4.dylib
  /usr/local/lib/libtcmalloc_minimal_debug.4.dylib

Warning: Unbrewed header files were found in /usr/local/include.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected header files:
  /usr/local/include/google/heap-checker.h
  /usr/local/include/google/heap-profiler.h
  /usr/local/include/google/malloc_extension.h
  /usr/local/include/google/malloc_extension_c.h
  /usr/local/include/google/malloc_hook.h
  /usr/local/include/google/malloc_hook_c.h
  /usr/local/include/google/profiler.h
  /usr/local/include/google/stacktrace.h
  /usr/local/include/google/tcmalloc.h
  /usr/local/include/gperftools/heap-checker.h
  /usr/local/include/gperftools/heap-profiler.h
  /usr/local/include/gperftools/malloc_extension.h
  /usr/local/include/gperftools/malloc_extension_c.h
  /usr/local/include/gperftools/malloc_hook.h
  /usr/local/include/gperftools/malloc_hook_c.h
  /usr/local/include/gperftools/nallocx.h
  /usr/local/include/gperftools/profiler.h
  /usr/local/include/gperftools/stacktrace.h
  /usr/local/include/gperftools/tcmalloc.h

Warning: Unbrewed '.la' files were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected '.la' files:
  /usr/local/lib/libprofiler.la
  /usr/local/lib/libtcmalloc.la
  /usr/local/lib/libtcmalloc_and_profiler.la
  /usr/local/lib/libtcmalloc_debug.la
  /usr/local/lib/libtcmalloc_minimal.la
  /usr/local/lib/libtcmalloc_minimal_debug.la

Warning: Unbrewed static libraries were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected static libraries:
  /usr/local/lib/libprofiler.a
  /usr/local/lib/libtcmalloc.a
  /usr/local/lib/libtcmalloc_and_profiler.a
  /usr/local/lib/libtcmalloc_debug.a
  /usr/local/lib/libtcmalloc_minimal.a
  /usr/local/lib/libtcmalloc_minimal_debug.a

Warning: You have unlinked kegs in your Cellar.
Leaving kegs unlinked can lead to build-trouble and cause formulae that depend on
those kegs to fail to run properly once built. Run `brew link` on these:
  python-jinja
  python-certifi
  languagetool
  python-packaging
  pycodestyle
  docker
  pygments
  python-dateutil
  python-requests
  ipython
  python-argcomplete
  python-urllib3
  python-psutil
  r
  the_platinum_searcher
  numpy
  emacs
  emacs-mac
  pyyaml
  python-typing-extensions
  doxygen
  jupyterlab
  python-charset-normalizer
  black
  jasper
  protobuf
  python-markupsafe

### Output of `brew tap`

```shell
brew tap
aconchillo/guile
aljohri/-
colindean/fonts-nonfree
craftamap/tap
cyclone-scheme/cyclone
github/gh
homebrew/bundle
homebrew/cask
homebrew/cask-fonts
homebrew/cask-versions
homebrew/core
homebrew/services
jakehilborn/jakehilborn
mht208/formal
michaelballantyne/vicare
microsoft/git
nuspell/nuspell
railwaycat/emacsmacport
xenodium/macosrec
zegervdv/zathura

[SMillerDev]

Does it exist after an install from upstream?

[jasonhemann]

Yes.

[jhemann:MacOS] 16:14:43$ pwd
/Volumes/Slic3r/Slic3r.app/Contents/MacOS
[jhemann:MacOS] 16:14:48$ ./Slic3r --version
1.3.0