Replace index_in_[sub]str_array with index_in_[sub]strings,

which scans thru "abc\0def\0123\0\0" type strings. Saves 250 bytes.

   text    data     bss     dec     hex filename
 781266    1328   11844  794438   c1f46 busybox_old
 781010    1328   11844  794182   c1e46 busybox_unstripped

coreutils/mv.c

@@ -24,7 +24,7 @@
 static const char mv_longopts[] =
 	"interactive\0" No_argument "i"
 	"force\0"       No_argument "f"
-	"\0";
+	;
 #endif
 
 #define OPT_FILEUTILS_FORCE       1