public void addBlobEntry(Blob blob, long size, String name, Instant modificationTime) {
    TarArchiveEntry entry = new TarArchiveEntry(name);
    entry.setSize(size);
    entry.setModTime(modificationTime.toEpochMilli());
    archiveMap.put(entry, blob);
  }
Adds a blob to the archive. Note that this should be used with non-file {@link Blob}s; for
adding files to the archive, use {@link #addTarArchiveEntry}.

@param blob the {@link Blob} to add to the tarball
@param size the size (in bytes) of {@code blob}
@param name the name of the entry (i.e. filename)
@param modificationTime the modification time of the entry
jib-core/src/main/java/com/google/cloud/tools/jib/tar/TarStreamBuilder.java