waf: make options groups accessible for any tool

That allows options being declared where they're really used. Additionally, we
load ardupilotwaf after the other tools so that we can create our groups after
all non-ardupilot option groups are created. That makes our groups appear as
the last ones in the help message, which makes it easier to locate them.

Tools/ardupilotwaf/ardupilotwaf.py

@@ -307,7 +307,7 @@ def _select_programs_from_group(bld):
             bld.targets += ',' + tg.name
 
 def options(opt):
-    g = opt.add_option_group('Ardupilot build options')
+    g = opt.ap_groups['build']
     g.add_option('--program-group',
         action='append',
         default=[],

wscript

@@ -39,10 +39,17 @@ def init(ctx):
         c.variant = env.BOARD
 
 def options(opt):
-    opt.load('ardupilotwaf')
     opt.load('compiler_cxx compiler_c waf_unit_test python')
 
-    g = opt.add_option_group('Ardupilot configure options')
+    opt.ap_groups = {
+        'configure': opt.add_option_group('Ardupilot configure options'),
+        'build': opt.add_option_group('Ardupilot build options'),
+        'check': opt.add_option_group('Ardupilot check options'),
+    }
+
+    opt.load('ardupilotwaf')
+
+    g = opt.ap_groups['configure']
     boards_names = boards.get_boards_names()
     g.add_option('--board',
                    action='store',
@@ -50,7 +57,7 @@ def options(opt):
                    default='sitl',
                    help='Target board to build, choices are %s' % boards_names)
 
-    g = opt.add_option_group('Ardupilot check options')
+    g = opt.ap_groups['check']
     g.add_option('--check-verbose',
                  action='store_true',
                  help='Output all test programs')