I tried to build it on OS X, had Qt 5.5.1 installed, and qmake ended normally, but make went terribly wrong, several errors occurred, not sure it's clang's fault or something else.

authcookiejar.cpp:34:12: error: use of overloaded operator '<<' is ambiguous (with operand types 'QDataStream' and 'const unsigned int')
stream << JAR_VERSION;

authcookiejar.cpp:35:12: error: use of overloaded operator '<<' is ambiguous (with operand types 'QDataStream' and 'quint32' (aka 'unsigned int'))
stream << quint32(list.size());

authcookiejar.cpp:46:12: error: invalid operands to binary expression ('QDataStream' and 'quint32' (aka 'unsigned int'))
stream >> version;

authcookiejar.cpp:52:12: error: invalid operands to binary expression ('QDataStream' and 'quint32' (aka 'unsigned int'))
stream >> count;

authcookiejar.cpp:63:19: error: member access into incomplete type 'QDataStream'
if (stream.atEnd());