waf: boards: bind get_board() to configure and build contexts

A convenience, since we don't expect the board to change for a given
configuration.

Tools/Replay/wscript

@@ -4,8 +4,7 @@
 import boards
 
 def build(bld):
-    board = boards.get_board(bld.env.BOARD)
-    if not isinstance(board, boards.linux):
+    if not isinstance(bld.get_board(), boards.linux):
         return
 
     bld.ap_program(

Tools/ardupilotwaf/boards.py

@@ -5,6 +5,7 @@ from collections import OrderedDict
 import sys
 
 import waflib
+from waflib.Configure import conf
 
 _board_classes = {}
 
@@ -160,10 +161,13 @@ def get_boards_names():
     return sorted(list(_board_classes.keys()))
 
 _board = None
-def get_board(name):
+@conf
+def get_board(ctx):
     global _board
     if not _board:
-        _board = _board_classes[name]()
+        if not ctx.env.BOARD:
+            ctx.fatal('BOARD environment variable must be set before first call to get_board()')
+        _board = _board_classes[ctx.env.BOARD]()
     return _board
 
 # NOTE: Keeping all the board definitions together so we can easily

Tools/ardupilotwaf/gtest.py

@@ -11,7 +11,7 @@ from waflib.Configure import conf
 import boards
 
 def configure(cfg):
-    board = boards.get_board(cfg.env.BOARD)
+    board = cfg.get_board()
     if isinstance(board, boards.px4):
         # toolchain is currently broken for gtest
         cfg.msg(

wscript

@@ -92,7 +92,7 @@ def configure(cfg):
     cfg.define('WAF_BUILD', 1)
 
     cfg.msg('Setting board to', cfg.options.board)
-    boards.get_board(cfg.env.BOARD).configure(cfg)
+    cfg.get_board().configure(cfg)
 
     cfg.load('clang_compilation_database')
     cfg.load('waf_unit_test')
@@ -266,7 +266,7 @@ def build(bld):
     _build_dynamic_sources(bld)
 
     bld.add_group('build')
-    boards.get_board(bld.env.BOARD).build(bld)
+    bld.get_board().build(bld)
     _build_common_taskgens(bld)
 
     _build_recursion(bld)