GPAC renamed its libraries to `libgpac.so.13` causing image build to fail:
```
Error: building at STEP "COPY --from=builder /usr/local/lib/libgpac.so.12 /usr/local/lib/": checking on sources under "/home/pszemus/.local/share/containers/storage/overlay/faa4f2b5c39251a5cf42a97234d2d5652336a2388c96a64d85fc1922c4c43a71/merged": copier: stat: "/usr/local/lib/libgpac.so.12": no such file or directory
```
so let's fix the gpac version to the latest release (2.4.0)
* [FIX] Corrected bitness check for 64-bit systems
* Improve Dockerfile: cleanup, parallel build, and remove redundancies
- Replaced cd with WORKDIR for clarity and Docker best practices.
- Removed unused LIB_CLANG_PATH export, as it only affected a single build layer; the library is automatically detected during build.
- Parallelized the GPAC build using make -j$(nproc).
- Removed redundant CMD instruction, as ENTRYPOINT already defines the container's execution command.
* [DOCS] Update CHANGES.TXT for Dockerfile improvements
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Co-authored-by: AhmedYasserrr <ahmdyasrj@gamil.com>