Check for ppoll() in toplevel wscript.

linux/wscript

@@ -1,9 +1,6 @@
 #! /usr/bin/env python
 # encoding: utf-8
 
-def configure(conf):
-    conf.define('HAVE_PPOLL', 1 )
-
 def create_jack_driver_obj(bld, target, sources, uselib = None):
     driver = bld(features = ['c', 'cxx', 'cxxshlib', 'cshlib'])
     driver.env['cxxshlib_PATTERN'] = 'jack_%s.so'

wscript

@@ -480,9 +480,14 @@ def configure(conf):
     # configure all auto options
     configure_auto_options(conf)
 
+    # Check for functions.
+    conf.check_cc(
+        function_name='ppoll',
+        header_name=['poll.h', 'signal.h'],
+        defines=['_GNU_SOURCE'],
+        mandatory=False)
+
     conf.recurse('common')
-    if conf.env['IS_LINUX']:
-        conf.recurse('linux')
     if Options.options.dbus:
         conf.recurse('dbus')
         if conf.env['BUILD_JACKDBUS'] != True: