Empty files are installed if 7zip compression level is zero

Data files compressed with 7-Zip level "0" (which means "copy" method) will be installed as empty files. However, rising the compression level to "1" is just enough to fix the issue.

"Copy" method should be supported, though, as it is quite standard way of creating a 7-Zip file out of already-compressed files.

Test files created with following commands:
7za a -t7z -mx=0 packages/com.test/data/test0.7z testFile
7za a -t7z -mx=1 packages/com.test/data/test1.7z testFile