Use lib64 on linux, lib on OSX. (#46)

Author: dmjio

arrayfire.cabal

@@ -90,7 +90,15 @@ library
   default-language:
     Haskell2010
 
-  if (os(linux) || os(OSX)) && !flag(disable-default-paths)
+  if os(linux) && !flag(disable-default-paths)
+    include-dirs:
+      /opt/arrayfire/include
+    extra-lib-dirs:
+      /opt/arrayfire/lib64
+    ld-options:
+      -Wl,-rpath /opt/arrayfire/lib64
+
+  if os(OSX) && !flag(disable-default-paths)
     include-dirs:
       /opt/arrayfire/include
     extra-lib-dirs: