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

diff --git a/util-linux/fdisk.c b/util-linux/fdisk.c
index 9f30571..01c01bd 100644
--- a/util-linux/fdisk.c
+++ b/util-linux/fdisk.c
@@ -2735,7 +2735,7 @@
 }
 #endif
 
-int fdisk_main(int argc, char **argv);
+int fdisk_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int fdisk_main(int argc, char **argv)
 {
 	char *str_b, *str_C, *str_H, *str_S;