Add noX11 flag to Linux compilations

This allows users that are not using X11 to still compile the
application.

build_scripts/linux/build_linux.sh

@@ -9,7 +9,7 @@ echo $MAKE_COMMAND
 mkdir -p $BUILD_DIR
 cd $BUILD_DIR
 qmake --version
-qmake -spec $QMAKE_SPEC $PROJECT_DIR
+qmake -spec $QMAKE_SPEC $PROJECT_DIR $QMAKE_EXTRAS
 $MAKE_COMMAND
 $CLANG_TIDY
 cp -r $PROJECT_DIR/src/res $BUILD_DIR/bin/linux/AdvancedSettings/

build_scripts/linux/configure.sh

@@ -18,3 +18,6 @@ else
     CLANG_TIDY="$SCRIPT_DIR/run-clang-tidy.sh"
 fi
 
+if [[ -n $NO_X11 ]]; then
+    QMAKE_EXTRAS='CONFIG+=noX11'
+fi