*: fix fallout from -Wunused-parameter

function                                             old     new   delta
bbunpack                                             358     366      +8
passwd_main                                         1070    1072      +2
handle_incoming_and_exit                            2651    2653      +2
getpty                                                88      86      -2
script_main                                          975     972      -3
inetd_main                                          2036    2033      -3
dname_enc                                            377     373      -4
make_new_session                                     474     462     -12
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/5 up/down: 12/-24)            Total: -12 bytes
   text    data     bss     dec     hex filename
 797429     658    7428  805515   c4a8b busybox_old
 797417     658    7428  805503   c4a7f busybox_unstripped

diff --git a/util-linux/fdisk.c b/util-linux/fdisk.c
index a75b4f8..dcfae96 100644
--- a/util-linux/fdisk.c
+++ b/util-linux/fdisk.c
@@ -128,7 +128,11 @@
 #endif
 static const char *partition_type(unsigned char type);
 static void get_geometry(void);
+#if ENABLE_FEATURE_SUN_LABEL || ENABLE_FEATURE_FDISK_WRITABLE
 static int get_boot(enum action what);
+#else
+static int get_boot(void);
+#endif
 
 #define PLURAL   0
 #define SINGULAR 1
@@ -1237,8 +1241,12 @@
  *    0: found or created label
  *    1: I/O error
  */
-static int
-get_boot(enum action what)
+#if ENABLE_FEATURE_SUN_LABEL || ENABLE_FEATURE_FDISK_WRITABLE
+static int get_boot(enum action what)
+#else
+static int get_boot(void)
+#define get_boot(what) get_boot()
+#endif
 {
 	int i;