waf: move SRCROOT env variable setting to common Board class

Tools/ardupilotwaf/boards.py

@@ -43,6 +43,9 @@ class Board:
         cfg.load('cxx_checks')
 
         env = waflib.ConfigSet.ConfigSet()
+        def srcpath(path):
+            return cfg.srcnode.make_node(path).abspath()
+        env.SRCROOT = srcpath('')
         self.configure_env(cfg, env)
 
         # Setup scripting, had to defer this to allow checking board size
@@ -592,10 +595,6 @@ class sitl(Board):
             env.CXXFLAGS += [
                 '-fno-slp-vectorize' # compiler bug when trying to use SLP
             ]
-        
-        def srcpath(path):
-            return cfg.srcnode.make_node(path).abspath()
-        env.SRCROOT = srcpath('')
 
 class sitl_periph_gps(sitl):
     def configure_env(self, cfg, env):