Setting 64-bit support in lib_dir for rhel/fedora correctly (before used).

Fixed issue where the variable lib_dir is used on line 31 but set (with 64-bit support) on line 37. Now set correctly before used.

Please see this comment and code for more context:
https://github.com/opscode-cookbooks/php/commit/78277fd9e2f02a9ce1f6a59bb64a755fcc4715c5#commitcomment-3283144