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

diff --git a/coreutils/whoami.c b/coreutils/whoami.c
index 3718358..e2fdfc9 100644
--- a/coreutils/whoami.c
+++ b/coreutils/whoami.c
@@ -13,7 +13,7 @@
 
 /* This is a NOFORK applet. Be very careful! */
 
-int whoami_main(int argc, char **argv);
+int whoami_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int whoami_main(int argc, char **argv)
 {
 	if (argc > 1)