libgluonutil: add missing libgen import (freifunk-gluon#3395)

The import of libgen.h required for basename() was missing. This lead to
undesired behavior on 64 bit systems, where only the upper 32-bit of the
returned pointer was used.

On ARM64 systems such as mediatek-filogic, this lead to a signed extend
of the 32-bit address, leading to a crash of respondd.

Signed-off-by: David Bauer <mail@david-bauer.net>

package/libgluonutil/src/libgluonutil.c

@@ -11,6 +11,7 @@
 
 #include <errno.h>
 #include <glob.h>
+#include <libgen.h>
 #include <limits.h>
 #include <stdio.h>
 #include <string.h>