bitbake.conf: Add SDK variable definitions

Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

meta/conf/bitbake.conf

@@ -30,6 +30,9 @@ export libdir = "${exec_prefix}/lib"
 export includedir = "${exec_prefix}/include"
 export oldincludedir = "${exec_prefix}/include"
 
+#
+# These must match the various bbclass layout definitions
+#
 base_bindir_native = "/bin"
 base_sbindir_native = "/sbin"
 sysconfdir_native = "/etc"