Installation error on El Capitan

```
› make build
go build -o build/git-lab
# gopkg.in/libgit2/git2go.v23
../../go/src/gopkg.in/libgit2/git2go.v23/diff.go:104: cannot use &hunk.header[0] (type *byte) as type *_Ctype_char in function argument
make: *** [build] Error 2
```

Any ideas on what went wrong?
