Enable more compiler warnings

src/common/dir.c

@@ -73,7 +73,7 @@ build_theme_path(struct ctx *ctx, char *prefix, const char *path)
 	}
 }
 
-char *
+static char *
 find_dir(struct ctx *ctx)
 {
 	char *debug = getenv("LABWC_DEBUG_DIR_CONFIG_AND_THEME");

src/common/scene-helpers.c

@@ -2,6 +2,7 @@
 
 #include <assert.h>
 #include <wlr/types/wlr_scene.h>
+#include "common/scene-helpers.h"
 
 struct wlr_scene_rect *
 lab_wlr_scene_get_rect(struct wlr_scene_node *node)

src/common/string-helpers.c

@@ -2,6 +2,7 @@
 #include <ctype.h>
 #include <stdio.h>
 #include <string.h>
+#include "common/string-helpers.h"
 
 static void
 rtrim(char **s)