fix: building with -flto=auto (#102)

I need this to finish the AUR packages at #100.

It probably also broke the current lidm-git package

src/ui.c

@@ -67,7 +67,7 @@ static void process_sigwinch(int signal) {
   need_resize = 1;
 }
 
-inline void draw_bg() {
+static inline void draw_bg() {
   // apply bg color to all screen
   printf("\x1b[%sm\x1b[2J", g_config->colors.bg);
 }