Building the tests for flex requires flex-native and bison-native, but the
attempt to add this dependency was done incorrectly. Use an inline python
conditional based on PTEST_ENABLED instead.
(From OE-Core rev: fce2be6dcf8e7320b7b9df9947745e78fd160815)
Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>