Canandian Cross Compiling and RTEMS 3rd party package building Fixes.

The change fixes installing for RTEMS 3rd Party packages where the
RSB considered them Canadian Cross Compiling (Cxc). Fixing the
Cxc issue broke real Cxc builds. The change corrects the issue of
macros being changed in the Cxc and the prep data not being udpated.
The configuration is loaded again after the updated macros. The
macros are also copied and restored to ensure a clean stable base.

The change also introduces --rtems-tools and --rtems-bsp to align
the command line with the waf configure process or RTEMS application.

source-builder/sb/path.py

@@ -201,7 +201,11 @@ def copy_tree(src, dst):
     if not os.path.isdir(hdst):
         if trace:
             print ' mkdir: %s' % (hdst)
-        os.makedirs(hdst)
+        try:
+            os.makedirs(hdst)
+        except OSError, why:
+            raise error.general('copying tree: cannot create target directory %s: %s' % \
+                                (hdst, str(why)))
 
     for name in names:
         srcname = host(os.path.join(hsrc, name))