Update QT6 in Compilation-Debian,-Ubuntu,-and-derivatives.md

[TheLQ]

Resolves #2 , qbittorrent/qBittorrent#22824 , qbittorrent/qBittorrent#21131, and half of qbittorrent/qBittorrent#21603 / #15

• Update qt6 packages
• libtorrent build uses ninja directly not cmake
• Addressed comment in Update Compilation-Debian,-Ubuntu,-and-derivatives.md for Qt versions #2

Testing

All-in-one Dockerfile builds a GUI successfully. Debian version GUI starts successfully.

Works for Debian Sid/Testing and Ubuntu Plucky (25.04)

FROM debian:sid
# FROM debian:bookworm
# FROM ubuntu:plucky

ADD libtorrent /work/libtorrent
ADD qBittorrent /work/qBittorrent

# Common build deps
RUN set -e -x && \
    echo 'Acquire::http::Proxy "http://192.168.66.11:3142";' > /etc/apt/apt.conf.d/99proxy && \
    apt-get update && \
    apt-get -y install build-essential cmake git ninja-build 
    # pkg-config 

# libtorrent
RUN set -e -x && \
    apt-get -y install libboost-dev libssl-dev 
RUN set -e -x && \
    cd /work/libtorrent && \
    cmake -B build -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_INSTALL_PREFIX=/usr/local -G Ninja && \
    cd build && \
    ninja && \
    ninja install

# qbittorrent
RUN set -e -x && \
    apt-get -y install --no-install-recommends  qt6-tools-dev qt6-base-dev qt6-base-private-dev qt6-svg-dev zlib1g-dev
    # libtorrent-rasterbar-dev
RUN set -e -x && \
    cd /work/qBittorrent && \
    cmake -B build -G "Ninja" -DCMAKE_BUILD_TYPE=Release -DWEBUI=ON -DGUI=ON -DTESTING=ON && \
    cmake --build build

[xavier2k6]

@TheLQ Thank you!