FreeBSD unrar cffi installation instructions

When doing the pip -r install requirements.txt, FBSD users will most likely receive an error pertaining to unrarsrc not being able to build and failing on unrar-cffi installation (or not being able to locate a package). Thanks to @btxgit and @ryusaku for working thru this and testing it, this seems to be the work-thru:

1. Download the src file here: most recent source of unrar-cffi

2. Install the gmake package if required: pkg install gmake (note this might not be necessary on some systems)

3. Unzip the src file somewhere and change (cd) into the directory

4. This can be done in 2 different ways:

   • From the command line: MAKE=gmake python setup.py build

     ---OR---

   • Edit buildconf.py

     • change [getenv("MAKE", 'make') ... ---> [getenv("MAKE", 'gmake') ....
     • then save/overwrite the buildconf.py file

5. python setup.py build

6. python setup.py install

to test, go into a command line python prompt:

import unrar.cffi

(if it comes back with an error, it's not installed. If it just goes to the next line, it's installed).