CMakeFile cannot find 'pthread_create'

cmake CMakeLIst.txt

CMake command after Error log
```
Determining if the pthread_create exist failed with the following output:
Change Dir: /home/eos/Documents/eos.tools/eos-vm/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_5200c/fast"
/usr/bin/make -f CMakeFiles/cmTC_5200c.dir/build.make CMakeFiles/cmTC_5200c.dir/build

make[1]: Entering directory '/home/eos/Documents/eos.tools/eos-vm/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_5200c.dir/CheckSymbolExists.c.o
/usr/bin/cc -o CMakeFiles/cmTC_5200c.dir/CheckSymbolExists.c.o -c /home/eos/Documents/eos.tools/eos-vm/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTC_5200c
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_5200c.dir/link.txt --verbose=1
/usr/bin/cc CMakeFiles/cmTC_5200c.dir/CheckSymbolExists.c.o -o cmTC_5200c
CMakeFiles/cmTC_5200c.dir/CheckSymbolExists.c.o: In function `main':
CheckSymbolExists.c:(.text+0x1b): undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
CMakeFiles/cmTC_5200c.dir/build.make:97: recipe for target 'cmTC_5200c' failed
make[1]: *** [cmTC_5200c] Error 1
make[1]: Leaving directory '/home/eos/Documents/eos.tools/eos-vm/CMakeFiles/CMakeTmp'
Makefile:126: recipe for target 'cmTC_5200c/fast' failed
make: *** [cmTC_5200c/fast] Error 2

File /home/eos/Documents/eos.tools/eos-vm/CMakeFiles/CMakeTmp/CheckSymbolExists.c:
/* */
#include

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/eos/Documents/eos.tools/eos-vm/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_6007c/fast"
/usr/bin/make -f CMakeFiles/cmTC_6007c.dir/build.make CMakeFiles/cmTC_6007c.dir/build
make[1]: Entering directory '/home/eos/Documents/eos.tools/eos-vm/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_6007c.dir/CheckFunctionExists.c.o
/usr/bin/cc -DCHECK_FUNCTION_EXISTS=pthread_create -o CMakeFiles/cmTC_6007c.dir/CheckFunctionExists.c.o -c /usr/share/cmake-3.10/Modules/CheckFunctionExists.c
Linking C executable cmTC_6007c
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_6007c.dir/link.txt --verbose=1
/usr/bin/cc -DCHECK_FUNCTION_EXISTS=pthread_create CMakeFiles/cmTC_6007c.dir/CheckFunctionExists.c.o -o cmTC_6007c -lpthreads
/usr/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
CMakeFiles/cmTC_6007c.dir/build.make:97: recipe for target 'cmTC_6007c' failed
make[1]: *** [cmTC_6007c] Error 1
make[1]: Leaving directory '/home/eos/Documents/eos.tools/eos-vm/CMakeFiles/CMakeTmp'
Makefile:126: recipe for target 'cmTC_6007c/fast' failed
make: *** [cmTC_6007c/fast] Error 2

```

Why CMake compile failed?