Thanks, does the following patch fix things for you?
If so, I'll install it into gnulib.
diff --git a/lib/sys_select.in.h b/lib/sys_select.in.h
index 28a3dac..061ebaf 100644
--- a/lib/sys_select.in.h
+++ b/lib/sys_select.in.h
@@ -19,14 +19,16 @@
# endif
@PRAGMA_COLUMNS@
-/* On OSF/1 and Solaris 2.6, <sys/types.h> and <sys/time.h>
+/* On many BSDish systems, <sys/types.h> and <sys/time.h>
both include <sys/select.h>.
On Cygwin, <sys/time.h> includes <sys/select.h>.
Simply delegate to the system's header in this case. */
#if (@HAVE_SYS_SELECT_H@ \
&& ((defined __osf__ && defined _SYS_TYPES_H_ \
- && !defined _GL_SYS_SELECT_H_REDIRECT_FROM_SYS_TIME_H \
+ && !defined _GL_SYS_SELECT_H_REDIRECT_FROM_SYS_TYPES_H \
&& defined _OSF_SOURCE) \
+ || ((defined __FreeBSD__ || defined __OpenBSD__) \
+ && defined _SYS_TYPES_H && __BSD_VISIBLE) \
|| (defined __sun && defined _SYS_TYPES_H \
&& (! (defined _XOPEN_SOURCE || defined _POSIX_C_SOURCE) \
|| defined __EXTENSIONS__))))
@@ -39,6 +41,9 @@
|| (defined __osf__ && defined _SYS_TIME_H_ \
&& !defined _GL_SYS_SELECT_H_REDIRECT_FROM_SYS_TIME_H \
&& defined _OSF_SOURCE) \
+ || (defined __FreeBSD__ && defined _SYS_TIME_H) \
+ || (defined __OpenBSD__ && defined _SYS_TIME_H \
+ && 420 <= __XPG_VISIBLE && __XPG_VISIBLE < 600) \
|| (defined __sun && defined _SYS_TIME_H \
&& (! (defined _XOPEN_SOURCE || defined _POSIX_C_SOURCE) \
|| defined __EXTENSIONS__))))
