component/firewalld: Strictly enforce make's PYTHON value

In some contexts (like package building) the top-make is called like:

  make -C slapos build PYTHON=/usr/bin/python2.7

And the value somehow poisons child make of this component, that even
overriding it with environment is not enough, thus strictly enforce it
during build of this component.

component/firewalld/buildout.cfg

@@ -71,6 +71,9 @@ configure-options =
   --disable-static
   --with-python=${buildout:executable}
 
+make-options =
+  PYTHON=${buildout:executable}
+
 environment =
   PATH=${pkgconfig:location}/bin:${gettext:location}/bin:${glib:location}/bin:${xz-utils:location}/bin:${flex:location}/bin:${bison:location}/bin:%(PATH)s
   PKG_CONFIG_PATH=${glib:location}/lib/pkgconfig:${pcre:location}/lib/pkgconfig