serf1: re-enable universal variant

[ryandesign (Ryan Carsten Schmidt)]

r108691 updated serf1 to 1.3.0 and switched to its scons build system, which brought with it use_configure no, which removes the universal variant, thereby dooming all ports depending on serf1 to non-universality. Please reinstate the universal variant.

At minimum, you'll need to add this line before the first time you invoke the get_canonical_archflags proc:

variant universal {}

However that alone does not appear to be sufficient. The port tries to communicate the archflags to the build system via the ARCHFLAGS environment variable, but grepping the serf source for ARCHFLAGS does not reveal any hits, so I'm not sure whether this is intended to work. (Is this a standard scons environment variable?)

My own opinion is that the scons build system is difficult to use, especially in MacPorts. That might be partially remedied by the creation of a scons portgroup to abstract away some of the implementation details.