On a rebuild base.bbclass will invoke "make clean" to ensure that old build
objects are not used. This will delete docstrings.c and the only way to
re-generate that is with a dedicated setup.py target.
(From OE-Core rev: f5bc0ba35ac531feae2e84bbc4f9d16f861db6c6)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>