Resolve symbolic links when checking for destination locations in file_packager. Fixes browser.test_preload_file on OSX.
Support syntax --preload-file x@x where both sides are identical and outside the current source tree. The code would accidentally treat that case as if user had instead written '--preload-file x'. Closes #2201.
Merge pull request #2206 from juj/fix_osx_test_preload_file

Resolve symbolic links when checking for destination locations in file_packager. Fixes browser.test_preload_file on OSX.