• SignTool crashes with "Unknown file format" / "Image is too small" when processing RPM, DEB, tar.gz, or PKG files containing symbolic links. For RPMs, the CPIO symlink entry's DataStream contains the link target path as text (e.g., mscorlib.dll), which gets passed to IsSignedPE() and fails. For tar/DEB, symlinks have null DataStream and are silently skipped, but should be explicitly filtered. For PKGs, Directory.EnumerateFiles returns symlinks as regular files.
• Skip symbolic links (and directories) when reading container entries for signing, and preserve them during repacking so the output container retains its original symlink structure pointing to the real signed files.
• Add symlink entries to test resource files (test.tgz, test.rpm, test.deb) and validate after signing+repacking that symlinks are preserved and resolve to the signed target files.
• pkg tests were not added at this point in time because of Add MacOS legs to CI #16519 and that I don't have access to a mac to run any tests locally.

Validated in the VMR with https://dev.azure.com/dnceng/internal/_build/results?buildId=2902616&view=results