THRIFT-4618: Use poll() instead of select() in C++ TNonblockingServer if available (#1580)

diff --git a/build/cmake/config.h.in b/build/cmake/config.h.in
index c5d4d30..39d8270 100644
--- a/build/cmake/config.h.in
+++ b/build/cmake/config.h.in
@@ -121,6 +121,9 @@
 /* Define to 1 if you have the <sys/un.h> header file. */
 #cmakedefine HAVE_SYS_UN_H 1
 
+/* Define to 1 if you have the <poll.h> header file. */
+#cmakedefine HAVE_POLL_H 1
+
 /* Define to 1 if you have the <sys/poll.h> header file. */
 #cmakedefine HAVE_SYS_POLL_H 1