Failure to package on FAT-family filesystems

[khionu]

Problem
Packaging on FAT-family filesystems fails on attempting to set the Modified Time.

Steps

1. Run cargo package on a FAT32 or exFAT filesystem

Possible Solution(s)
Take advantage of the flag added here.

[alexcrichton]

To add some more context, this started out as alexcrichton/filetime#30, went to alexcrichton/tar-rs#169, and culminated in alexcrichton/tar-rs@f442964.

The problem here is that not all filesystems allow configuring the mtime (for whatever reason), but Cargo tries to set the mtime of files when it extracts them from a tarball. Cargo doesn't actually really need to do that though, so it should be easy enough to simply call set_preserve_mtime(false) on tarball extraction