waf --apiscan will no longer try to abort waf build at the end of scanning, to avoid the waf hang. Fixes #1622.

bindings/python/wscript

@@ -310,7 +310,7 @@ def get_module_path(bld, module):
         raise ValueError("Module %r not found" % module)
     return ns3headers.path.abspath()
 
-class apiscan_task(Task.TaskBase):
+class apiscan_task(Task.Task):
     """Uses gccxml to scan the file 'everything.h' and extract API definitions.
     """
     after = 'gen_ns3_module_header ns3header'
@@ -318,7 +318,7 @@ class apiscan_task(Task.TaskBase):
     color = "BLUE"
     def __init__(self, curdirnode, env, bld, target, cflags, module):
         self.bld = bld
-        super(apiscan_task, self).__init__(generator=self)
+        super(apiscan_task, self).__init__(generator=self, env=env)
         self.curdirnode = curdirnode
         self.env = env
         self.target = target
@@ -341,6 +341,8 @@ class apiscan_task(Task.TaskBase):
             return self.uid_
 
     def run(self):
+        self.inputs = [self.bld.bldnode.find_resource("ns3/{0}-module.h".format(self.module))]
+        self.outputs = [self.bld.srcnode.find_resource("src/{}/bindings/modulegen__{}.py".format(self.module, self.target))]
         top_builddir = self.bld.bldnode.abspath()
         module_path = get_module_path(self.bld, self.module)
         headers_map = get_headers_map(self.bld)
@@ -393,30 +395,6 @@ def get_modules_and_headers(bld):
 
 
 
-class python_scan_task_collector(Task.TaskBase):
-    """Tasks that waits for the python-scan-* tasks to complete and then signals WAF to exit
-    """
-    after = 'apiscan'
-    before = 'cxx'
-    color = "BLUE"
-    def __init__(self, curdirnode, env, bld):
-        self.bld = bld
-        super(python_scan_task_collector, self).__init__(generator=self)
-        self.curdirnode = curdirnode
-        self.env = env
-
-    def display(self):
-        return 'python-scan-collector\n'
-
-    def run(self):
-        # signal stop (we generated files into the source dir and WAF
-        # can't cope with it, so we have to force the user to restart
-        # WAF)
-        self.bld.producer.stop = 1
-        return 0
-
-
-
 class gen_ns3_compat_pymod_task(Task.Task):
     """Generates a 'ns3.py' compatibility module."""
     before = 'cxx'
@@ -479,7 +457,6 @@ def build(bld):
             group = bld.get_group(bld.current_group)
             for module in scan_modules:
                 group.append(apiscan_task(bld.path, env, bld, target, cflags, module))
-        group.append(python_scan_task_collector(bld.path, env, bld))
         return