synergy 1.4.16 fails to compile - undefined reference to `pthread_xxxx' - c++

Question

When attempting to compile synergy 1.4.16 on a Mint 17.1 (Rebecca) I get the following error:
../../../../../lib/libarch.a(CArchMultithreadPosix.o): In function `CArchMultithreadPosix::newMutex()':
CArchMultithreadPosix.cpp:(.text+0x319): undefined reference to `pthread_mutexattr_init'
../../../../../lib/libarch.a(CArchMultithreadPosix.o): In function `CArchMultithreadPosix::raiseSignal(IArchMultithread::ESignal)':
CArchMultithreadPosix.cpp:(.text+0x43b): undefined reference to `pthread_kill'
../../../../../lib/libarch.a(CArchMultithreadPosix.o): In function `CArchMultithreadPosix::threadSignalHandler(void*)':
CArchMultithreadPosix.cpp:(.text+0x490): undefined reference to `pthread_detach'
../../../../../lib/libarch.a(CArchMultithreadPosix.o): In function `CArchMultithreadPosix::closeThread(CArchThreadImpl*)':
CArchMultithreadPosix.cpp:(.text+0x62b): undefined reference to `pthread_detach'
../../../../../lib/libarch.a(CArchMultithreadPosix.o): In function `CArchMultithreadPosix::newThread(void* (*)(void*), void*)':
CArchMultithreadPosix.cpp:(.text+0x8e6): undefined reference to `pthread_sigmask'
CArchMultithreadPosix.cpp:(.text+0x90f): undefined reference to `pthread_sigmask'
CArchMultithreadPosix.cpp:(.text+0x935): undefined reference to `pthread_create'
CArchMultithreadPosix.cpp:(.text+0x9a4): undefined reference to `pthread_create'
../../../../../lib/libarch.a(CArchMultithreadPosix.o): In function `CArchMultithreadPosix::CArchMultithreadPosix()':
CArchMultithreadPosix.cpp:(.text+0xe11): undefined reference to `pthread_mutexattr_init'
CArchMultithreadPosix.cpp:(.text+0xf05): undefined reference to `pthread_sigmask'
CArchMultithreadPosix.cpp:(.text+0xf26): undefined reference to `pthread_sigmask'
../../../../../lib/libarch.a(CArchMultithreadPosix.o): In function `CArchMultithreadPosix::startSignalHandler()':
CArchMultithreadPosix.cpp:(.text+0x10a8): undefined reference to `pthread_sigmask'
CArchMultithreadPosix.cpp:(.text+0x10cd): undefined reference to `pthread_sigmask'
CArchMultithreadPosix.cpp:(.text+0x1104): undefined reference to `pthread_create'
../../../../../lib/libarch.a(CArchMultithreadPosix.o): In function `CArchMultithreadPosix::cancelThread(CArchThreadImpl*)':
CArchMultithreadPosix.cpp:(.text+0x5e3): undefined reference to `pthread_kill'
collect2: error: ld returned 1 exit status
make[2]: *** [../../bin/synergyd] Error 1
make[1]: *** [src/cmd/synergyd/CMakeFiles/synergyd.dir/all] Error 2
make: *** [all] Error 2
Going back to: /home/jussi/Downloads/synergy-1.4.16/synergy-1.4.16-Source
Error: make failed: 512
I already tried the solution to the identical problem here but the solution of adding pthreadto the end of target_link_libraries on src/cmd/synergyd/CMakeLists.txt does not resolve my issue, it remains the same.
The only reason I'm not using pre-compiled packages is that I need to use synergy with my Raspberry Pi 3 and the packages available through the packge repos have incompatible synergy protocols - 1.4.16 on Pi vs 1.4.12 on Mint 17.1 so an alternative solution to have compatible protocols on each of the machines will also be sufficient.

Answer 1

Setting CMAKE_CXX_FLAGS after project definition in CMakeList.txt made it to work for me:
First, declare project (important for prerequisite checks).
project(synergy C CXX)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++03 -pthread")

Answer 2

Identified an alternative solution: I worked my way around this by (ab?)using the fact that the synergy server with higher protocol version seems to be backwards-compatible with older protocol versions, so I compiled the version 1.8.something and the client on my Pi with 1.4.16 is happy to connect and I can now share the keyboard and mouse connected to my Mint with the Pi.