main': CheckSymbolExists.c:(.text+0x1b): undefined reference to pthread_create - c++

Question

I am building Faunus software using cmake with command -->
$cmake . -DENABLE_OPENMP=ON -DENABLE_PYTHON=ON -DCMAKE_INSTALL_PREFIX:PATH=/home/user/localInstall/tstFaunusInstOpenMP -DPYTHON_EXECUTABLE=/home/user/anaconda3/envs/faunus-env/bin/python3.6 -DPYTHON_INCLUDE_DIR=/home/user/anaconda3/envs/faunus-env/include/python3.6m -DPYTHON_LIBRARY=/home/user/anaconda3/envs/faunus-env/lib -DCMAKE_CXX_FLAGS_DEBUG="-pthread"
I am getting build error like :
Determining if the pthread_create exist failed with the following output:
Change Dir: /home/user/softwares/openMPfaunus-2.4.1/CMakeFiles/CMakeTmp
Run Build Command:"/usr/bin/make" "cmTC_a43c8/fast"
/usr/bin/make -f CMakeFiles/cmTC_a43c8.dir/build.make CMakeFiles/cmTC_a43c8.dir/build
make[1]: Entering directory '/home/user/softwares/openMPfaunus-2.4.1/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_a43c8.dir/CheckSymbolExists.c.o
/usr/bin/cc -o CMakeFiles/cmTC_a43c8.dir/CheckSymbolExists.c.o -c /home/user/softwares/openMPfaunus-2.4.1/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTC_a43c8
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_a43c8.dir/link.txt --verbose=1
/usr/bin/cc CMakeFiles/cmTC_a43c8.dir/CheckSymbolExists.c.o -o cmTC_a43c8
/usr/bin/ld: CMakeFiles/cmTC_a43c8.dir/CheckSymbolExists.c.o: in function `main':
CheckSymbolExists.c:(.text+0x1b): undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
make[1]: *** [CMakeFiles/cmTC_a43c8.dir/build.make:87: cmTC_a43c8] Error 1
make[1]: Leaving directory '/home/user/softwares/openMPfaunus-2.4.1/CMakeFiles/CMakeTmp'
make: *** [Makefile:121: cmTC_a43c8/fast] Error 2
File /home/user/softwares/openMPfaunus-2.4.1/CMakeFiles/CMakeTmp/CheckSymbolExists.c:
/* */
#include <pthread.h>
int main(int argc, char** argv)
{
(void)argv;
#ifndef pthread_create
return ((int*)(&pthread_create))[argc];
#else
(void)argc;
return 0;
#endif
}
##############################################################
What I could understand from this is that there is section of file "CheckSymbolExists.c", which requires pthread_create. I wrote a simple code in C and ran using option: gcc example.c -lm -pthread and it's is working fine but if I run without -pthread option I am getting the same error concerning pthread_create.
Can someone help out this.