POSIX OSAL: snprintf overlaps destination

[tbouvencourt]

Describe the bug
The issue occurs in: osal/src/os/posix/src/os-impl-filesys.c
Function : OS_FileSysStartVolume_Impl()

Compilation error :

error: ‘snprintf’ argument 5 overlaps destination object ‘OS_filesys_table’ [-Werror=restrict]
176 | snprintf(local->system_mountpt, sizeof(local->system_mountpt),
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
177 | "%s/osal:%s", tmpdir, local->volume_name);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To Reproduce
Following : Exercise 1 – Build and Run the cFE (from training document)

System observed on:

• OS: PRETTY_NAME="Debian GNU/Linux 13 (trixie)"
  NAME="Debian GNU/Linux"
• GCC : gcc (Debian 14.2.0-19) 14.2.0

Recommendation
Introduce a temporary local copy