Require CMake 3.4 and use the OpenSSL imported libs

Summary:
Fixes
00:09:45.140 [162/278] Linking CXX shared module lib/qca-qt5/crypto/libqca-ossl.dylib
00:09:45.140 FAILED: lib/qca-qt5/crypto/libqca-ossl.dylib
00:09:45.140 : && /usr/bin/clang++ -O2 -g -DNDEBUG -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -bundle -Wl,-headerpad_max_install_names -o lib/qca-qt5/crypto/libqca-ossl.dylib plugins/qca-ossl/CMakeFiles/qca-ossl.dir/qca-ossl.cpp.o lib/qca-qt5.framework/Versions/2.2.0/qca-qt5 /Users/packaging/Craft/BinaryCache/macos-64-clang/lib/libssl.dylib /Users/packaging/Craft/BinaryCache/macos-64-clang/lib/libcrypto.dylib -lcrypto /Users/packaging/Craft/BinaryCache/macos-64-clang/lib/QtCore.framework/QtCore -framework CoreFoundation -framework Security && :
00:09:45.140 ld: library not found for -lcrypto
00:09:45.140 clang: error: linker command failed with exit code 1 (use -v to see invocation)

Reviewers: dfaure, bcooksley, volkov

Reviewed By: dfaure

Differential Revision: https://phabricator.kde.org/D17913