This fixes a problem visible when installing openssl 1.1.1d from
component/openssl. At the end of install step, some symlinks are created
inside openssl install directory for all certificates from
ca-certificates part, then the "make read only" step occurs, which
recursively chmod on files and folder in openssl installed parts, but
since this was following symlinks, it was also trying to make readonly
in ca-certificates parts, which in my case was belonging to another
unix user, because it was a shared part folder from outer level slapos.

/reviewed-on nexedi/slapos.recipe.build!10

download, downloadunpacked: Check shared directory is not enough. Shared directory may be created before completing installation. Check signature file too.

Revert "download, downloadunpacked: Check shared directory is not enough. Shared directory may be created before completing installation. Check signature file too."

This reverts commit 9be7928b.

download, downloadunpacked: Check shared directory is not enough. Shared directory may be created before completing installation. Check signature file too.

downloadunpacked: Because shared part should not be uninstalled, install method should return an empty list in shared mode.

download, downloadunpacked: Rename 'shared-part' to 'shared-parts'. Since the original option name is 'parts', 'shared-parts' is consistent.

download, downloadunpacked: Disable shared feature by default since it is stil an experimental one. Enable it only if shared-part is defined.

setuptools.archive_util is not available unless setuptools.archive_util
have been imported before.

For example:
```python
>>> import setuptools
>>> setuptools.archive_util
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'archive_util'
>>> import setuptools.archive_util
>>> setuptools.archive_util
<module 'setuptools.archive_util' from '/usr/local/lib/python2.7/dist-packages/setuptools/archive_util.pyc'>
```

/reviewed-on nexedi/slapos.recipe.build!3

Not fully tested. With this commit, it is at least possible to
bootstrap SlapOS from Python 3.

Squashed commit of the following:

commit 506d815ff7e1d7b7b5b3c5edcfcea744c5b2201e
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 17:54:59 2011 +0200

    Support multiline values.

commit c5d9415000fb072a07164bbdd5c276e53470b265
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 17:48:54 2011 +0200

    Fix compatibility layer.

commit 1e301c7ba51060d944fea9ff2be1aba00e3a48b6
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 17:41:41 2011 +0200

    Go back to development.

commit 9f523c49
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 17:40:00 2011 +0200

    Prepare 0.5 release.

commit fcaf5c04
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 17:39:28 2011 +0200

    Be more compatible.

commit 5284491f
Merge: 2d7dc0b3 f15bb155
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 17:28:40 2011 +0200

    Merge branch 'master' into cmmi

commit 2d7dc0b3
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 17:22:13 2011 +0200

    Explain more about patches.

commit d5df4cdc
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 17:18:55 2011 +0200

    Provide better looking patches.

commit c6befb05
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 17:15:32 2011 +0200

    Support make-command and make-options.

    Fix configure-command.

commit d2212cb7
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 17:04:05 2011 +0200

    Allow to override configure command.

commit 4321b38a
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:56:49 2011 +0200

    Share applyPatchList with in base class.

commit 4a2ea3b3
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:56:29 2011 +0200

    Support no md5sum.

commit 2cd36cb7
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:56:16 2011 +0200

    Show how to patch.

commit 8cd9ea9c
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:53:45 2011 +0200

    Allow options per patch.

commit 84fea623
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:48:47 2011 +0200

    Allow patching.

commit 8934eb92
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:30:46 2011 +0200

    Allow to keep directories in case of error.

    Default is to remove.

commit 74d0b2bd
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:24:49 2011 +0200

    Allow to have a=b=c, where a is key and b=c is value.

commit 034c2381
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:17:07 2011 +0200

    Another typo.

commit f5abcde0
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:15:44 2011 +0200

    Follow fixed typo.

commit 5b950e26
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:14:35 2011 +0200

    Extract does not need md5sum.

commit 6f725632
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:14:14 2011 +0200

    Pass md5sum directly.

commit 9f42d22a
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:13:53 2011 +0200

    Allow to pass empty md5sum.

commit c91fafb1
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:13:15 2011 +0200

    Fix typos.

commit 8919378d
Author: Łukasz Nowak <luke@nexedi.com>
Date:   Tue Sep 6 16:12:31 2011 +0200

    Fix examples.

slapos.cookbook provided it before, but it is simple functionality, which does
not need so many dependencies.