Add the support using system-wide installed capstone library

the capstone has been installed in system,so I don't want build capstone again when build from source.

In some reason(china), it's too slow to download capstone T_T...you know what I means...

Start by locating the build setup that downloads and builds Capstone, then inspect how an installed system library could be detected and selected instead. Done means a source build can use the system-wide Capstone installation without downloading or rebuilding it; verify the relevant build configuration and installation path.

Written by the indexing model from the issue text.