Allow failure of sighandler installation on NativeClient.

* signal.c (install_signalhandler, init_sigchld): allow failure because it
  always fails with ENOSYS on NaCl.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47873 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

io.c

@@ -204,6 +204,9 @@ rb_update_max_fd(int fd)
     }
 }
 
+#undef HAVE_FCNTL
+#undef O_CLOEXEC
+
 void
 rb_maygvl_fd_fix_cloexec(int fd)
 {

signal.c

@@ -1261,7 +1261,9 @@ install_sighandler(int signum, sighandler_t handler)
     rb_enable_interrupt();
     return 0;
 }
+#ifndef __native_client__
 #  define install_sighandler(signum, handler) (install_sighandler(signum, handler) ? rb_bug(#signum) : (void)0)
+#endif
 
 #if defined(SIGCLD) || defined(SIGCHLD)
 static int
@@ -1281,8 +1283,10 @@ init_sigchld(int sig)
     rb_enable_interrupt();
     return 0;
 }
+#  ifndef __native_client__
 #    define init_sigchld(signum) (init_sigchld(signum) ? rb_bug(#signum) : (void)0)
 #  endif
+#endif
 
 void
 ruby_sig_finalize(void)