XCB plugin doesn't build because of missing -lXExt

make[6]: Leaving directory '/home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel/qt5-5.8.0-beta/qtbase/src/plugins/platforms/xcb/xcb-static'
( test -e Makefile.xcb_qpa_lib || /home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel/qt5-5.8.0-beta/qtbase/bin/qmake -o Makefile.xcb_qpa_lib /home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel/qt5-5.8.0-beta/qtbase/src/plugins/platforms/xcb/xcb_qpa_lib.pro -qtconf /home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel/qt5-5.8.0-beta/qtbase/bin/qt.conf -- -sysroot /home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel/toolchain/x86_64-libreelec-linux-gnu/sysroot -prefix /usr/local/qt5 -hostprefix /home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel -device-option CROSS_COMPILE=/home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel/toolchain/bin/x86_64-libreelec-linux-gnu- -device linux-Generic-g++ -release -v -opensource -confirm-license -shared -make libs -no-pch -no-icu -qt-xkbcommon -no-sql-sqlite2 -nomake examples -nomake tests -no-libjpeg -qpa xcb -opengl desktop -no-kms -no-directfb -qt-xcb -skip qtactiveqt -skip qtandroidextras -skip qtdoc -skip qtvirtualkeyboard -skip qtcharts -skip qtdatavis3d -skip qtgraphicaleffects -skip qtlocation -skip qtmacextras -skip qtscript -skip qtsensors -skip qtserialport -skip qtcanvas3d -skip qtwayland -skip qtwinextras -skip qtserialbus -skip qtxmlpatterns -skip qttranslations -skip qtmultimedia -skip qtscxml -skip qtquickcontrols2 -skip qt3d -skip qtpurchasing -skip qtgamepad -skip qtwebview --force-debug-info ) && make -f Makefile.xcb_qpa_lib
make[6]: Entering directory '/home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel/qt5-5.8.0-beta/qtbase/src/plugins/platforms/xcb'
rm -f libQt5XcbQpa.so.5.8.0 libQt5XcbQpa.so libQt5XcbQpa.so.5 libQt5XcbQpa.so.5.8
/home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel/toolchain/bin/x86_64-libreelec-linux-gnu-g++ -m64 -fPIC --sysroot=/home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel/toolchain/x86_64-libreelec-linux-gnu/sysroot -Wl,--no-undefined -Wl,--version-script,QtXcbQpa.version -fuse-ld=gold -Wl,--enable-new-dtags -Wl,-z,origin -Wl,-rpath,\$ORIGIN -shared -Wl,-Bsymbolic-functions -Wl,-soname,libQt5XcbQpa.so.5 -o libQt5XcbQpa.so.5.8.0 .obj/qxcbclipboard.o .obj/qxcbconnection.o .obj/qxcbintegration.o .obj/qxcbkeyboard.o .obj/qxcbmime.o .obj/qxcbdrag.o .obj/qxcbscreen.o .obj/qxcbwindow.o .obj/qxcbbackingstore.o .obj/qxcbwmsupport.o .obj/qxcbnativeinterface.o .obj/qxcbcursor.o .obj/qxcbimage.o .obj/qxcbxsettings.o .obj/qxcbsystemtraytracker.o .obj/qxcbconnection_xi2.o .obj/qxcbglintegrationfactory.o .obj/qxcbglintegration.o .obj/qxcbnativeinterfacehandler.o .obj/atom.o .obj/xkb-compat.o .obj/context.o .obj/xkb-keymap.o .obj/keysym.o .obj/keysym-utf.o .obj/state.o .obj/text.o .obj/context-priv.o .obj/keymap-priv.o .obj/utils.o .obj/utf8.o .obj/action.o .obj/ast-build.o .obj/compat.o .obj/expr.o .obj/include.o .obj/keycodes.o .obj/keymap-dump.o .obj/keymap.o .obj/keywords.o .obj/rules.o .obj/scanner.o .obj/symbols.o .obj/types.o .obj/vmod.o .obj/xkbcomp.o .obj/parser.o .obj/moc_qxcbconnection.o .obj/moc_qxcbmime.o .obj/moc_qxcbnativeinterface.o .obj/moc_qxcbsystemtraytracker.o .obj/moc_qxcbglintegrationplugin.o  -L/home/longchair/LibreELEC.tv/build.PlexMediaPlayer-Generic.x86_64-8.0-devel/qt5-5.8.0-beta/qtbase/lib -lQt5ServiceSupport -lQt5ThemeSupport -lQt5EventDispatcherSupport -lgthread-2.0 -lglib-2.0 -lQt5FontDatabaseSupport -lQt5LinuxAccessibilitySupport -lQt5AccessibilitySupport -lGL -lQt5Gui -lQt5DBus -lQt5Core -lpthread -lX11 -lX11-xcb -lXi -lxcb-static -lxcb -lfontconfig -lfreetype -lGL
/tmp/cc950ijS.ltrans1.ltrans.o:<artificial>:function _XiCheckExtInit: error: undefined reference to 'XMissingExtension'
/tmp/cc950ijS.ltrans1.ltrans.o:<artificial>:function XInput_find_display: error: undefined reference to 'XextFindDisplay'
/tmp/cc950ijS.ltrans1.ltrans.o:<artificial>:function XInput_find_display: error: undefined reference to 'XextCreateExtension'
/tmp/cc950ijS.ltrans1.ltrans.o:<artificial>:function XInput_find_display: error: undefined reference to 'XextAddDisplay'
/tmp/cc950ijS.ltrans1.ltrans.o:<artificial>:function XInputClose: error: undefined reference to 'XextRemoveDisplay'
/tmp/cc950ijS.ltrans1.ltrans.o:<artificial>:function XInputClose: error: undefined reference to 'XextDestroyExtension'