fix copying symlinks with relative paths in copyDirSyncRecursive

- you have a file: common/foo.js
- you have another directory (not_common/stuff/) and you add a symlink in it (../../common/foo.js)
- you use copyDirSyncRecursive to copy the directory 'stuff' somewhere else (not_common/not_stuff/build/target)
- it will copy the sym link with the same relative path (../../common/foo.js) which is not valid

this fix creates an absolute path link instead
Merge pull request #23 from johnwana/master

Broken symlinks possible when copying symlinks with relative paths in copyDirSyncRecursive