Determining if the pthread_create exist failed with the following output:
Change Dir: /ascldap/users/tesari/lynx/build/ews_gcc6_mpich321/ep_cmt/CMakeFiles/CMakeTmp

Run Build Command(s):/opt/rh/devtoolset-6/root/usr/bin/gmake cmTC_61f42/fast 
gmake[3]: Entering directory '/home/tesari/lynx/build/ews_gcc6_mpich321/ep_cmt/CMakeFiles/CMakeTmp'
/opt/rh/devtoolset-6/root/usr/bin/gmake -f CMakeFiles/cmTC_61f42.dir/build.make CMakeFiles/cmTC_61f42.dir/build
gmake[4]: Entering directory '/home/tesari/lynx/build/ews_gcc6_mpich321/ep_cmt/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_61f42.dir/CheckSymbolExists.c.o
/ascldap/users/tesari/local/mpich-3.2.1_gcc-6.3/bin/mpicc    -o CMakeFiles/cmTC_61f42.dir/CheckSymbolExists.c.o   -c /ascldap/users/tesari/lynx/build/ews_gcc6_mpich321/ep_cmt/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTC_61f42
/ascldap/users/tesari/local/cmake/3.14.4/bin/cmake -E cmake_link_script CMakeFiles/cmTC_61f42.dir/link.txt --verbose=1
/ascldap/users/tesari/local/mpich-3.2.1_gcc-6.3/bin/mpicc      CMakeFiles/cmTC_61f42.dir/CheckSymbolExists.c.o  -o cmTC_61f42 
/opt/rh/devtoolset-6/root/usr/libexec/gcc/x86_64-redhat-linux/6.3.1/ld: CMakeFiles/cmTC_61f42.dir/CheckSymbolExists.c.o: undefined reference to symbol 'pthread_create@@GLIBC_2.2.5'
//lib64/libpthread.so.0: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
CMakeFiles/cmTC_61f42.dir/build.make:86: recipe for target 'cmTC_61f42' failed
gmake[4]: *** [cmTC_61f42] Error 1
gmake[4]: Leaving directory '/home/tesari/lynx/build/ews_gcc6_mpich321/ep_cmt/CMakeFiles/CMakeTmp'
Makefile:121: recipe for target 'cmTC_61f42/fast' failed
gmake[3]: *** [cmTC_61f42/fast] Error 2
gmake[3]: Leaving directory '/home/tesari/lynx/build/ews_gcc6_mpich321/ep_cmt/CMakeFiles/CMakeTmp'

File /ascldap/users/tesari/lynx/build/ews_gcc6_mpich321/ep_cmt/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
}