Upgrade iOS build script to use venv

.github/autobuild/ios.sh

@@ -26,7 +26,7 @@
 
 set -eu
 
-QT_DIR=/usr/local/opt/qt
+QT_DIR=/opt/qt
 # The following version pinnings are semi-automatically checked for
 # updates. Verify .github/workflows/bump-dependencies.yaml when changing those manually:
 AQTINSTALL_VERSION=3.1.18
@@ -45,7 +45,15 @@ setup() {
         echo "Using Qt installation from previous run (actions/cache)"
     else
         echo "Installing Qt"
-        python3 -m pip install "aqtinstall==${AQTINSTALL_VERSION}"
+        # We may need to create the Qt installation directory and chown it to the runner user to fix permissions
+        sudo mkdir -p "${QT_DIR}"
+        sudo chown "$(whoami)" "${QT_DIR}"
+        # Create and enter virtual environment
+        python3 -m venv venv
+        # Must hide directory as it just gets created during execution of the previous command and cannot be found by shellcheck
+        # shellcheck source=/dev/null
+        source venv/bin/activate
+        pip install "aqtinstall==${AQTINSTALL_VERSION}"
         # Install actual ios Qt:
         local qtmultimedia=()
         if [[ ! "${QT_VERSION}" =~ 5\.[0-9]+\.[0-9]+ ]]; then
@@ -62,10 +70,9 @@ setup() {
             python3 -m aqt install-qt --outputdir "${QT_DIR}" mac desktop "${QT_VERSION}" --archives qtbase
         fi
 
-        # Suppress deprecation of Legacy Build System for now.
-        # TODO: Legacy Build System is removed in xcode 14. Need to migrate
-        # to the Modern Build System instead.
-        /usr/libexec/PlistBuddy -c "Add :DisableBuildSystemDeprecationDiagnostic bool true" /usr/local/opt/qt/"${QT_VERSION}"/ios/mkspecs/macx-xcode/WorkspaceSettings.xcsettings
+        # deactivate and remove venv as aqt is no longer needed from here on
+        deactivate
+        rm -rf venv
     fi
 }