Fix memory leak in binreloc function _br_find_exe()

Ironically, it seems to be in a code path that
is only followed when using valgrind

libgnucash/core-utils/binreloc.c

@@ -195,6 +195,7 @@ _br_find_exe (Gnc_GbrInitError *error)
 
     result = g_strdup (result);
     fclose (f);
+    g_free (line);
     return result;
 #endif /* ENABLE_BINRELOC */
 }