Missing pkg-config file

[radare]

No description provided.

[sakkaku]

I added pkg-config by emulating the method glew uses to generate the .pc file. https://github.com/sakkaku/libCello/commit/f833077d499fc6ed753ecbc42299826195e7f9f0

1. The cflags and ldflags needed varies based on compiler. This version jerks out the extra flags added for the platform and/or clang and throws it into the file. Theoretically "mixing" compilers from library installation and program compilation would result in a failed build.
2. I am not sure some flags are needed, for instance fPIC.
3. I need to redo it to where it doesn't override the .gitignore, maybe generate the .pc locally before it is pushed to prefix. I'm lazy >_<

[orangeduck]

I don't have any experience with pkg-config so can't give you much help with that, sorry!