py-borghash, missing BDEP

borghash uses cython if present during build. for consistency, I'd like
to list it as a BDEP. ok?

Index: Makefile
===================================================================
RCS file: /cvs/ports/devel/py-borghash/Makefile,v
diff -u -p -r1.5 Makefile
--- Makefile	9 Feb 2026 20:05:53 -0000	1.5
+++ Makefile	5 Aug 2026 16:59:24 -0000
@@ -1,6 +1,7 @@
 COMMENT =		memory-efficient hashtable with serialization
 
 MODPY_DISTV =		0.1.1
+REVISION =		0
 DISTNAME =		borghash-${MODPY_DISTV}
 PKGNAME =		py-${DISTNAME}
 
@@ -16,6 +17,9 @@ PERMIT_PACKAGE =	Yes
 MODULES =		lang/python
 MODPY_PYBUILD =		setuptools_scm
 MODPY_PI =		Yes
+
+# used if present at build time
+BUILD_DEPENDS =		lang/cython
 
 # tests not included in pypi tarball
 NO_TEST	=		Yes