math/py-contourpy: unbreak build with non-default python (+)

Countourpy fails to find versioned pybind11-config which leads to configure error

pybind11-config found: NO
Did not find CMake 'cmake'
Found CMake: NO
Run-time dependency pybind11 found: NO (tried pkgconfig and config-tool)

../meson.build:23:15: ERROR: Dependency "pybind11" not found, tried pkgconfig and config-tool

Fix it by providing BINARY_ALIAS

Reported by:	poudriere failure
Approved by:	portmgr blanket

math/py-contourpy/Makefile

@@ -20,4 +20,6 @@ TEST_DEPENDS=	${PYTHON_PKGNAMEPREFIX}matplotlib>=0:math/py-matplotlib@${PY_FLAVO
 USES=		pkgconfig python
 USE_PYTHON=	autoplist concurrent pep517 pytest
 
+BINARY_ALIAS=	pybind11-config=pybind11-config-${PYTHON_VER}
+
 .include <bsd.port.mk>