Gitlab CI: Use Qt6 with Ubuntu builds

Our ubuntu container has Qt6 so use the default Qt version.

The APT packages are still using Qt5 at the moment. We may want to
migrate those to Qt6 in the future and choose a single Linux build
using Qt5.

.gitlab-ci.yml

@@ -118,7 +118,7 @@ variables:
   script:
     # setcap restricts our library paths
     - printf "\e[0Ksection_start:%s:cmake_section[collapsed=true]\r\e[0KRunning CMake" "$( date +%s)"
-    - CFLAGS=-Wl,-rpath=$(pwd)/run CXXFLAGS=-Wl,-rpath=$(pwd)/run cmake -GNinja -DENABLE_CCACHE=ON -DUSE_qt6=OFF $CMAKE_ARGS ..
+    - CFLAGS=-Wl,-rpath=$(pwd)/run CXXFLAGS=-Wl,-rpath=$(pwd)/run cmake -GNinja -DENABLE_CCACHE=ON $CMAKE_ARGS ..
     - printf "\e[0Ksection_end:%s:cmake_section\r\e[0K" "$( date +%s)"
     - ninja
     - ninja install
@@ -187,7 +187,7 @@ Source Package:
   script:
     - ../tools/make-version.py --set-release ..
     - printf "\e[0Ksection_start:%s:cmake_section[collapsed=true]\r\e[0KRunning CMake" "$( date +%s)"
-    - cmake -G Ninja $CMAKE_ARGS -DENABLE_CCACHE=ON -DUSE_qt6=OFF ..
+    - cmake -G Ninja $CMAKE_ARGS -DENABLE_CCACHE=ON ..
     - printf "\e[0Ksection_end:%s:cmake_section\r\e[0K" "$( date +%s)"
     - cd $CI_PROJECT_DIR
     - build/packaging/source/git-export-release.sh -d .
@@ -453,7 +453,7 @@ Documentation:
     - mkdir build
     - cd build
     - printf "\e[0Ksection_start:%s:cmake_section[collapsed=true]\r\e[0KRunning CMake" "$( date +%s)"
-    - cmake -GNinja -DUSE_qt6=OFF ..
+    - cmake -GNinja ..
     - printf "\e[0Ksection_end:%s:cmake_section\r\e[0K" "$( date +%s)"
     - ninja all_guides
     - cd docbook
@@ -505,7 +505,7 @@ GCC Warnings:
   script:
     # build-ubuntu puts us in `build`.
     - printf "\e[0Ksection_start:%s:cmake_section[collapsed=true]\r\e[0KRunning CMake" "$( date +%s)"
-    - CC=gcc CXX=g++ cmake -DENABLE_EXTRA_COMPILER_WARNINGS=on -DCMAKE_EXPORT_COMPILE_COMMANDS=on -DENABLE_CCACHE=ON -DUSE_qt6=OFF -G Ninja ..
+    - CC=gcc CXX=g++ cmake -DENABLE_EXTRA_COMPILER_WARNINGS=on -DCMAKE_EXPORT_COMPILE_COMMANDS=on -DENABLE_CCACHE=ON -G Ninja ..
     - printf "\e[0Ksection_end:%s:cmake_section\r\e[0K" "$( date +%s)"
     - script --command ninja --flush --quiet --return ../gcc_report.txt
     - ansi2html < ../gcc_report.txt > ../gcc_report.html
@@ -535,7 +535,7 @@ Code Checks + Clang Warnings:
     - cd build
     - printf "\e[0Ksection_start:%s:cmake_section[collapsed=true]\r\e[0KRunning CMake" "$( date +%s)"
     # We don't have an "All options" job, so build fuzzshark and tfshark here.
-    - cmake -DENABLE_EXTRA_COMPILER_WARNINGS=on -DENABLE_CHECKHF_CONFLICT=on -DCMAKE_EXPORT_COMPILE_COMMANDS=on -DBUILD_fuzzshark=ON -DBUILD_tfshark=On -DBUILD_logray=ON -DENABLE_CCACHE=ON -DUSE_qt6=OFF -G Ninja ..
+    - cmake -DENABLE_EXTRA_COMPILER_WARNINGS=on -DENABLE_CHECKHF_CONFLICT=on -DCMAKE_EXPORT_COMPILE_COMMANDS=on -DBUILD_fuzzshark=ON -DBUILD_tfshark=On -DBUILD_logray=ON -DENABLE_CCACHE=ON -G Ninja ..
     - printf "\e[0Ksection_end:%s:cmake_section\r\e[0K" "$( date +%s)"
     - mkdir ../html
     - script --command ninja --flush --quiet --return ../tmp_clang_report.txt
@@ -560,7 +560,7 @@ No options:
   extends: .build-ubuntu
   rules: !reference [.if-merge-request]
   script: |
-    cmake -GNinja -DENABLE_CCACHE=ON -DUSE_qt6=OFF \
+    cmake -GNinja -DENABLE_CCACHE=ON \
       -DENABLE_BROTLI=OFF -DENABLE_CAP=OFF -DENABLE_CARES=OFF -DENABLE_CHECKHF_CONFLICT=ON -DENABLE_GNUTLS=OFF \
       -DENABLE_KERBEROS=OFF -DENABLE_LIBXML2=OFF -DENABLE_ILBC=OFF -DENABLE_LUA=OFF -DENABLE_LZ4=OFF -DENABLE_MINIZIP=OFF \
       -DENABLE_NETLINK=OFF -DENABLE_NGHTTP2=OFF -DENABLE_PCAP=OFF -DENABLE_PLUGIN_IFDEMO=ON -DENABLE_PLUGINS=OFF \
@@ -610,7 +610,7 @@ Coverity GCC Scan:
     - tar --directory=/tmp --extract --gzip --file /tmp/cov-analysis-linux64.tar.gz
     - mkdir build
     - cd build
-    - cmake -G Ninja -DUSE_qt6=OFF ..
+    - cmake -G Ninja ..
     - /tmp/cov-analysis-linux64-*/bin/cov-build --return-emit-failures --dir ../cov-int ninja
     - cd ..
     - tar --create --gzip --file cov-int.tar.gz cov-int
@@ -682,7 +682,7 @@ Clang Static Analyzer:
     CC: "clang-${CLANG_VERSION}"
     CXX: "clang++-${CLANG_VERSION}"
   script:
-    - scan-build-${CLANG_VERSION} cmake -DCMAKE_BUILD_TYPE=Debug -DENABLE_WERROR=OFF -DUSE_qt6=OFF -G Ninja ..
+    - scan-build-${CLANG_VERSION} cmake -DCMAKE_BUILD_TYPE=Debug -DENABLE_WERROR=OFF -G Ninja ..
     - scan-build-${CLANG_VERSION} -o ../sbout ninja
     - cd ../sbout
     - RAW_DIR=$( find ../sbout -type d -name "20??-??-??-*" -printf "%P\n" | head )
@@ -714,7 +714,7 @@ API Reference:
   rules: !reference [.if-daily-schedule]
   script:
     - printf "\e[0Ksection_start:%s:cmake_section[collapsed=true]\r\e[0KRunning CMake" "$( date +%s)"
-    - cmake -GNinja -DUSE_qt6=OFF ..
+    - cmake -GNinja ..
     - printf "\e[0Ksection_end:%s:cmake_section\r\e[0K" "$( date +%s)"
     - ninja wsar_html_zip 2>&1 > doxygen_output.txt | tee doxygen_errors.txt
   after_script:
@@ -752,7 +752,7 @@ Code Lines:
     - tar -xf tokei-x86_64-unknown-linux-gnu.tar.gz
     - popd
     - printf "\e[0Ksection_start:%s:cmake_section[collapsed=true]\r\e[0KRunning CMake" "$( date +%s)"
-    - cmake -G Ninja -DUSE_qt6=OFF ..
+    - cmake -G Ninja ..
     - printf "\e[0Ksection_end:%s:cmake_section\r\e[0K" "$( date +%s)"
     - ninja
     - cd ..