sigil: fix arch handling

[ryandesign@…]

sigil has a section "platform x86_64". There is no such platform in MacPorts so this part of the portfile should be removed. In fact the whole way the port deals with architectures should be revisited. Instead of platform statements, you should be using ${build_arch} (and if you want to support universal builds, ${universal_archs}). The ui_msgs in pre-configure should be examined as well and probably removed. You may also want to switch to using the cmake portgroup instead of handling cmakeisms manually.

[jmr@…]

r85251