Configure CMake to build statically linked binaries

[jonas]

In order to make it easy to generate bindings, users should be able to automatically download the binary from the GitHub release page or via an sbt plugin.

[kornilova203]

Currently executable has following dependencies:

$ ldd scala-native-bindgen
        linux-vdso.so.1 =>  (0x00007ffec3bcb000)
        libLLVM-4.0.so.1 => /usr/lib/llvm-4.0/lib/libLLVM-4.0.so.1 (0x00007f8f16849000)
        libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f8f164c3000)
        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f8f162ac000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f8f15ecc000)
        libffi.so.6 => /usr/lib/x86_64-linux-gnu/libffi.so.6 (0x00007f8f15cc4000)
        libedit.so.2 => /usr/lib/x86_64-linux-gnu/libedit.so.2 (0x00007f8f15a8d000)
        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f8f15889000)
        libtinfo.so.5 => /lib/x86_64-linux-gnu/libtinfo.so.5 (0x00007f8f15660000)
        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f8f15441000)
        libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f8f15224000)
        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f8f14ece000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f8f1aae3000)

[jonas]

I found this PR which uses llvm-config to resolve libraries: https://github.com/ponylang/ponyc/pull/2425/files