capstone: directory install fix

Deals with the issues seen in #34316. 

Forces a recompile as well, since anyone who has this package installed from bottle has only text files in the Cellar, and anyone who has the package installed from source has ``` /usr/local ``` full of stuff that shouldn’t be directly there.
I don't know why I went for the shell command rather than going Ruby native. That was clumsy of me, heh.