Fix bugs in tde_create_tarball macro #15

When I try to use macro in knights module, I found two bugs. Both are fixed by this patch.

looks good

Tar command in cmake 2.8 does not allow all the options that we used. Therefore, further changes are needed.

The first part of the problem was discovered – in older CMake it is not possible to use -- for separating parameters from the file list for the tar command. After removing -- from parameters, the tarball is successfully created.

However, I have identified a second problem, which is why we probably have to use system tar instead of the CMake command tar. The files are packaged in the tar archive with the current owner / group, which means, for example, on my builder that they are owned by the user and the group pbuilder.

Using external tar brings another problem. We need to finding out what implementation is available.

GNU tar has parameters --owner=… --group=…
BSD tar has parameters --uname=… --gname=…

I thought this is default behavior: "[...] on my builder that they are owned by the user and the group pbuilder"

When you are not root it uses always the user, when you untar from that it will set the user with which you untar. Why should this be not acceptable?

When you untar as root ... you'll get the user that corresponds to the id that had 'pbuilder' or you'll see the id if such user does not exist.

I am consider myself newbie, but I was reading recently the specs of add_custom_command and discovered the ARGS argument. So what happens if you write something like

COMMAND ${CMAKE_COMMAND} 
   ARGS -E tar "cfz" "${CMAKE_CURRENT_BINARY_DIR}/${_target}" -- ${_files}

this was in cmake 3.0.2 doc

The point is that a pure chroot is usually used when building packages, where the source files are unpacked with a some working UID / user name. The resulting binary packages should not refer to "some working UID" from the chroot that can be associated with a real user on users machines. Therefore, we need that the tarballs created during the build would refer to user root, instead of to some working UID / user name.

Mentioned -- should serve not for CMake, but for tar as a separator beetween tar options and file list. The CMake option ARGS therefore has a different purpose and is not a solution here.

From commit d9d9396324, instead of the CMake tar command, system tar is used. This allows to add parameters for setting the files owner in tarball – the syntax for GNU tar and BSD tar is supported.

An option has been added to determine the compression program – gzip is as default.