Confirmed on master, this define allows input.c to compile

diff --git a/lib/readline/input.c b/lib/readline/input.c
index 44d14872..bf3424c1 100644
--- a/lib/readline/input.c
+++ b/lib/readline/input.c
@@ -79,7 +79,7 @@ extern int errno;
 #  define O_NDELAY O_NONBLOCK  /* Posix style */
 #endif
 
-#if defined (HAVE_PSELECT)
+#if defined (HAVE_PSELECT) || defined (HAVE_SELECT)
 extern sigset_t _rl_orig_sigset;
 #endif
 
@@ -805,7 +805,7 @@ rl_getc (FILE *stream)
   int result;
   unsigned char c;
   int fd;
-#if defined (HAVE_PSELECT)
+#if defined (HAVE_PSELECT) || defined(HAVE_SELECT)
   sigset_t empty_set;
   fd_set readfds;
 #endif

This was reported to the mailing list from what I can tell, but the code has changed so this issue reappeared.