(PUP-2912) PMT Build symlink exception

Prior to this commit the build command would add symlinks to packages. This
can cause unexpected behavior when installed on a system.
This commit causes the build command to throw an error when it finds a symlink.
That should prevent new modules from being created with a symlink included.
(PE-2912) Error on symlink in module install

Prior to this commit when encountering a symlink in a module file during install,
the install would error out with No such file or directory - /path/to/symlink.
This is confusing and doesn't show what the problem actually is.
This commit modifies the installer behavior to check for any symlinks after the
module is extracted, give errors for each symlink it finds, and die. This will
hopefully help module authors track down the actual reason for the failed install
more easily.
(PUP-2912) Builder/unpacker spec tests

Adding spec tests to check for symlinks in build/install.
Merge pull request #2854 from highb/fix/master/pup-2912_build_no_symlinks

(PUP-2912) PMT Build symlink exception