add -fvisibility=hidden to CC flags, mark XXX_main functions
EXTERNALLY_VISIBLE. 5% size reduction of libbusybox.so

diff --git a/networking/hostname.c b/networking/hostname.c
index 6783dba..2c224be 100644
--- a/networking/hostname.c
+++ b/networking/hostname.c
@@ -42,7 +42,7 @@
 	}
 }
 
-int hostname_main(int argc, char **argv);
+int hostname_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int hostname_main(int argc, char **argv)
 {
 	enum {