Updating wscripts to use custom tasks

src/kernel/wscript

@@ -19,10 +19,25 @@ def build(bld):
         linkflags = "-T {}".format(lds),
     )
 
-    bld(
-        source = bld.env.KERNEL_FILENAME,
-        target = "{}/kernel.dump".format(bld.out_dir),
-        rule = "objdump -D ${SRC} > ${TGT}",
-    )
+    from waflib.Task import Task
+    class objdump(Task):
+        color = 'PINK'
+        def keyword(self):
+            return "Dumping"
+        def __str__(self):
+            node = self.outputs[0]
+            return node.path_from(node.ctx.launch_node())
+        def run(self):
+            from subprocess import check_output
+            args = self.env.objdump + ["-D", self.inputs[0].abspath()]
+            with file(self.outputs[0].abspath(), 'w') as output:
+                output.write(check_output(args))
+
+    out = bld.path.get_bld()
+
+    dump = objdump(env=bld.env)
+    dump.set_inputs([out.make_node(bld.env.KERNEL_FILENAME)])
+    dump.set_outputs([out.make_node("kernel.dump")])
+    bld.add_to_group(dump)
 
 # vim: ft=python et