$ ./bin/crystal build -o .build/crystal_cyg src/compiler/crystal.cr --target x86_64-apple-darwin16.1.0
Using compiled compiler at .build/crystal
using path x86_64-apple-darwin16.1.0
Error while requiring "prelude"

in src/prelude.cr:15: while requiring "exception"

require "exception"
^

in src/exception.cr:1: while requiring "callstack"

require "callstack"
^

in src/callstack.cr:1: while requiring "c/dlfcn": can't find file 'c/dlfcn' relative to '/Users/packrd/dev/ruby/downloads/crystal/src'

require "c/dlfcn"
^