I have some fix to build ios sdk from scratch (OSX 10.8 and Xcode 4.6.3) with enable_gpl_third_parties=yes and enable_zrtp=yes.
Two different problems: first, the output name of the zrtp library is libzrtpcppcore but some makefile search libzrtpcpp, then:
ln -sf libzrtpcppcore.pc liblinphone-sdk/armv7-apple-darwin/lib/pkgconfig/libzrtpcpp.pc
ln -sf libzrtpcppcore.pc liblinphone-sdk/armv7s-apple-darwin/lib/pkgconfig/libzrtpcpp.pc
ln -sf libzrtpcppcore.pc liblinphone-sdk/i386-apple-darwin/lib/pkgconfig/libzrtpcpp.pc
Second problem is the dependency from openssl, I had to install openssl with universal flag:
sudo port install openssl +universal
and I have created this symbolic links:
ln -sf /opt/local/lib/pkgconfig/libcrypto.pc liblinphone-sdk/armv7-apple-darwin/lib/pkgconfig/libcrypto.pc
ln -sf /opt/local/lib/pkgconfig/libcrypto.pc liblinphone-sdk/armv7s-apple-darwin/lib/pkgconfig/libcrypto.pc
ln -sf /opt/local/lib/pkgconfig/libcrypto.pc liblinphone-sdk/i386-apple-darwin/lib/pkgconfig/libcrypto.pc
I hope this can help.