Determining if the pthread_create exist failed with the following output:
Change Dir: /home/builder/projects/OpenGLTests/build/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_749a1/fast"
/usr/bin/make -f CMakeFiles/cmTC_749a1.dir/build.make CMakeFiles/cmTC_749a1.dir/build
make[1]: Entering directory '/home/builder/projects/OpenGLTests/build/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_749a1.dir/CheckSymbolExists.c.o
/usr/bin/cc    -o CMakeFiles/cmTC_749a1.dir/CheckSymbolExists.c.o   -c /home/builder/projects/OpenGLTests/build/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTC_749a1
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_749a1.dir/link.txt --verbose=1
/usr/bin/cc      CMakeFiles/cmTC_749a1.dir/CheckSymbolExists.c.o  -o cmTC_749a1 
/usr/bin/ld: CMakeFiles/cmTC_749a1.dir/CheckSymbolExists.c.o: in function `main':
CheckSymbolExists.c:(.text+0x1f): undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
make[1]: *** [CMakeFiles/cmTC_749a1.dir/build.make:87: cmTC_749a1] Error 1
make[1]: Leaving directory '/home/builder/projects/OpenGLTests/build/CMakeFiles/CMakeTmp'
make: *** [Makefile:121: cmTC_749a1/fast] Error 2

File /home/builder/projects/OpenGLTests/build/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
}

Determining if the function pthread_create exists in the pthreads failed with the following output:
Change Dir: /home/builder/projects/OpenGLTests/build/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_e8785/fast"
/usr/bin/make -f CMakeFiles/cmTC_e8785.dir/build.make CMakeFiles/cmTC_e8785.dir/build
make[1]: Entering directory '/home/builder/projects/OpenGLTests/build/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_e8785.dir/CheckFunctionExists.c.o
/usr/bin/cc   -DCHECK_FUNCTION_EXISTS=pthread_create   -o CMakeFiles/cmTC_e8785.dir/CheckFunctionExists.c.o   -c /usr/share/cmake-3.13/Modules/CheckFunctionExists.c
Linking C executable cmTC_e8785
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_e8785.dir/link.txt --verbose=1
/usr/bin/cc  -DCHECK_FUNCTION_EXISTS=pthread_create    CMakeFiles/cmTC_e8785.dir/CheckFunctionExists.c.o  -o cmTC_e8785 -lpthreads 
/usr/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
make[1]: *** [CMakeFiles/cmTC_e8785.dir/build.make:87: cmTC_e8785] Error 1
make[1]: Leaving directory '/home/builder/projects/OpenGLTests/build/CMakeFiles/CMakeTmp'
make: *** [Makefile:121: cmTC_e8785/fast] Error 2