handle symlinks correctly when doing dir copy

[luogni]

Hi, I'm using nfpm to create deb packages from a full directory with lots of files and libraries (.so files).

contents:
  - src: /opt/gstreamer
    dst: /opt/gstreamer

Normal files are copied correctly but symlinks are transformed to normal files (dpkg -c file.deb):

-rwxr-xr-x root/root    121152 2021-12-17 16:06 ./opt/gstreamer/lib/libswresample.so
-rwxr-xr-x root/root    121152 2021-12-17 16:06 ./opt/gstreamer/lib/libswresample.so.3
-rwxr-xr-x root/root    121152 2021-12-17 16:06 ./opt/gstreamer/lib/libswresample.so.3.9.100

.so and .so.3 files should be symlinks. I can't specify every single symlink because there are tons of them.

[Felixoid]

I am trying to address the issue in goreleaser/fileglob#24 and #453