Put error message in the dynamically loading condition

Author: mrkn

RbCall.jl/src/prepare.jl

@@ -27,6 +27,7 @@ if !symbols_present
  script = joinpath(dirname(@__FILE__), "..", "ruby", "find_libruby.rb")
  cmd = `ruby $script`
  println(cmd)
+ error("Dynamically loading of libruby.so is not supported yet")
 else
  @static if Sys.iswindows()
  # TODO support windows
@@ -76,5 +77,3 @@ else
  :(cglobal(($(esc(sym)), libruby), VALUE))
  end
 end
-
-