[newlib-cygwin/main] libc/include/sys/select.h: Use elif not elifdef

[Joel Sherrill]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=176b19fbe5e77c4ee8199b3895d0299bd4f8267e

commit 176b19fbe5e77c4ee8199b3895d0299bd4f8267e
Author: Joel Sherrill <joel@rtems.org>
Date:   Wed Mar 13 09:29:36 2024 -0500

    libc/include/sys/select.h: Use elif not elifdef
    
    The cpp directive "elifdef" is only available in very recent GCC versions.
    This should be able to compile on older toolchains in C99 mode.`

Diff:
---
 newlib/libc/include/sys/select.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/newlib/libc/include/sys/select.h b/newlib/libc/include/sys/select.h
index 8b5675640..89269400b 100644
--- a/newlib/libc/include/sys/select.h
+++ b/newlib/libc/include/sys/select.h
@@ -30,7 +30,7 @@ typedef	__sigset_t	sigset_t;
 #ifndef FD_SETSIZE
 # ifdef __CYGWIN__
 #  define FD_SETSIZE	1024
-# elifdef __rtems__
+# elif defined(__rtems__)
 #  define FD_SETSIZE	256
 # else
 #  define FD_SETSIZE	64