CI/FreeBSD: switch TravisCI to Clang 11

.ci/install-freebsd.sh

@@ -8,12 +8,10 @@ sed -i '' 's/quarterly/latest/' /etc/pkg/FreeBSD.conf
 export ASSUME_ALWAYS_YES=true
 pkg info # debug
 
-# XXX Drop after Travis upgrades FreeBSD to 12.2 (see also .ci/build-freebsd.sh)
-case $(${CXX:-c++} --version) in
-    *version\ 8.0.*)
-	pkg install llvm10
-	;;
-esac
+# Prefer newer Clang on TravisCI (see also .ci/install-freebsd.sh)
+if [ -n "$TRAVIS" ]; then
+	pkg install llvm11
+fi
 
 # Mandatory dependencies (qt5-dbus and qt5-gui are pulled via qt5-widgets)
 pkg install git ccache cmake ninja qt5-qmake qt5-buildtools qt5-widgets qt5-concurrent glew openal-soft ffmpeg