Redirect all stderr messages to a single file

[tclahr]

UAC redirects stderr messages to individual .stderr files. This makes the analysis of error messages easier, but, depending on the system, it also pollutes the output file with tons of .stderr (for commands not found for instance).

The plan is to redirect all stderr messages to uac.log.stderr for instance, so all error messages would be placed in a single file.

[tclahr]

New code pushed to develop branch. stderr messages will no longer be recorded in individual .stderr files. Now they are all added to uac.log

If the executed command generates an error message (stderr), it will be recorded on the same line following the 2> identifier.

2024-05-23 18:07:44 -0300 CMD uptime -s 2> uptime: invalid option -- 's'/nTry 'uptime --help' for more information.
2024-05-23 18:08:04 -0300 CMD fdisk -l 2> fdisk: cannot open /dev/vda: Permission denied