waf: cmake: define proper uid() functions

The default implementation takes into account the task's output and input
nodes. That isn't very well applicable for cmake tasks, so we define proper
uid() methods.

Tools/ardupilotwaf/cmake.py

@@ -101,6 +101,18 @@ from collections import OrderedDict
 class cmake_configure_task(Task.Task):
     run_str = '${CMAKE} ${CMAKE_SRC_DIR} ${CMAKE_VARS} ${CMAKE_GENERATOR_OPTION}'
 
+    def uid(self):
+        if not hasattr(self, 'uid_'):
+            m = Utils.md5()
+            def u(s):
+                m.update(s.encode('utf-8'))
+            u(self.__class__.__name__)
+            u(self.env.get_flat('CMAKE_SRC_DIR'))
+            u(self.env.get_flat('CMAKE_BLD_DIR'))
+            self.uid_ = m.digest()
+
+        return self.uid_
+
     def __str__(self):
         return self.generator.name
 
@@ -110,6 +122,18 @@ class cmake_configure_task(Task.Task):
 class cmake_build_task(Task.Task):
     run_str = '${CMAKE} --build ${CMAKE_BLD_DIR} --target ${CMAKE_TARGET}'
 
+    def uid(self):
+        if not hasattr(self, 'uid_'):
+            m = Utils.md5()
+            def u(s):
+                m.update(s.encode('utf-8'))
+            u(self.__class__.__name__)
+            u(self.env.get_flat('CMAKE_BLD_DIR'))
+            u(self.env.get_flat('CMAKE_TARGET'))
+            self.uid_ = m.digest()
+
+        return self.uid_
+
     def __str__(self):
         config_name = self.generator.config_taskgen.name
         target = self.generator.cmake_target
@@ -147,6 +171,7 @@ def process_cmake_configure(self):
     # NOTE: we'll probably need to use the full class name in waf 1.9
     tsk = self.cmake_config_task = self.create_task('cmake_configure')
     tsk.cwd = self.cmake_bld.abspath()
+    tsk.env.CMAKE_BLD_DIR = self.cmake_bld.abspath()
     tsk.env.CMAKE_SRC_DIR = self.cmake_src.abspath()
 
     keys = list(self.cmake_vars.keys())