[Unix Build Actions] Do not preserve directory tree when packing tar (#334)

* Update linux.yml

Now it won't preserve the directory tree (i.e it won't include the "export/release/linux/bin" folders)

* do the same for macos

.github/workflows/linux.yml

@@ -36,7 +36,7 @@ jobs:
         run: |
           haxelib run lime build linux
       - name: Tar files
-        run: tar -zcvf CodenameEngine.tar.gz export/release/linux/bin
+        run: tar -zcvf CodenameEngine.tar.gz -C export/release/linux/bin .
       - name: Uploading artifact (entire build)
         uses: actions/upload-artifact@v2
         with: