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

diff --git a/shell/lash.c b/shell/lash.c
index b7a0a6a..ce1ce7f 100644
--- a/shell/lash.c
+++ b/shell/lash.c
@@ -1491,7 +1491,7 @@
 }
 #endif
 
-int lash_main(int argc_l, char **argv_l);
+int lash_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int lash_main(int argc_l, char **argv_l)
 {
 	unsigned opt;