databases/py-peewee: force cythonization

Remove pregenerated cython .c files to force regeneration. This
fixes build with python 3.9+, with which pregenerated files are not
compatible.

Approved by:	portmgr blanket

databases/py-peewee/Makefile

@@ -25,6 +25,9 @@ PYDISTUTILS_BUILD_TARGET=	build build_ext
 PYDISTUTILS_BUILDARGS+=	--include-dirs=${LOCALBASE}/include \
 			--library-dirs=${LOCALBASE}/lib
 
+post-extract:
+	@${RM} ${WRKSRC}/playhouse/*.c
+
 post-install:
 	@${STRIP_CMD} ${STAGEDIR}${PYTHONPREFIX_SITELIBDIR}/playhouse/*.so