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

diff --git a/coreutils/nohup.c b/coreutils/nohup.c
index e27bd2e..da8f58c 100644
--- a/coreutils/nohup.c
+++ b/coreutils/nohup.c
@@ -12,7 +12,7 @@
 
 #include "libbb.h"
 
-int nohup_main(int argc, char **argv);
+int nohup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int nohup_main(int argc, char **argv)
 {
 	int nullfd;