utils: Fix alias to weak alias to allow OSX compilation

Using a weak alias works just as good AFAICT.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/src/utils.c b/src/utils.c
index d32c5c0..0a970ac 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -180,7 +180,7 @@
 
 	/* Compat with previous typo to preserve abi */
 char *osmo_osmo_hexdump_nospc(const unsigned char *buf, int len)
-	__attribute__((alias("osmo_hexdump_nospc")));
+	__attribute__((weak, alias("osmo_hexdump_nospc")));
 
 #include "../config.h"
 #ifdef HAVE_CTYPE_H