basic + fundamental: Clean up includes

Split out of #37344.

src/basic/dlfcn-util.c

@@ -3,6 +3,14 @@
 #include "dlfcn-util.h"
 #include "log.h"
 
+void* safe_dlclose(void *dl) {
+        if (!dl)
+                return NULL;
+
+        assert_se(dlclose(dl) == 0);
+        return NULL;
+}
+
 static int dlsym_many_or_warnv(void *dl, int log_level, va_list ap) {
         void (**fn)(void);