Fix building service command with musl

Fix building the service command with musl libc by including the
missing libgen.h header to provide basename.

Bug: 190084016
Test: m USE_HOST_MUSL=true host-native
Change-Id: I10f33966969a84aa8839a133b965d4098e20df89
diff --git a/cmds/service/service.cpp b/cmds/service/service.cpp
index fe417a3..d5ca725 100644
--- a/cmds/service/service.cpp
+++ b/cmds/service/service.cpp
@@ -21,6 +21,7 @@
 #include <cutils/ashmem.h>
 
 #include <getopt.h>
+#include <libgen.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>