Handle interrupt on epoll_wait graciously (allows strace to work)

lib/pure/selectors.nim

@@ -146,7 +146,11 @@ elif defined(linux):
     ## on the ``fd``.
     result = @[]
     let evNum = epoll_wait(s.epollFD, addr s.events[0], 64.cint, timeout.cint)
-    if evNum < 0: raiseOSError(osLastError())
+    if evNum < 0:
+      let err = osLastError()
+      if err.cint == EINTR:
+        return @[]
+      raiseOSError(osLastError())
     if evNum == 0: return @[]
     for i in 0 .. <evNum:
       let fd = s.events[i].data.fd.SocketHandle