Performing C SOURCE FILE Test CMAKE_HAVE_LIBC_PTHREAD failed with the following output:
Change Dir: /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/gmake cmTC_36b86/fast && gmake[1]: Entering directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp'
/usr/bin/gmake  -f CMakeFiles/cmTC_36b86.dir/build.make CMakeFiles/cmTC_36b86.dir/build
gmake[2]: Entering directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_36b86.dir/src.c.o
/usr/bin/gcc   -O2 -I/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/host/include -DCMAKE_HAVE_LIBC_PTHREAD -o CMakeFiles/cmTC_36b86.dir/src.c.o -c /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp/src.c
Linking C executable cmTC_36b86
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_36b86.dir/link.txt --verbose=1
/usr/bin/gcc -O2 -I/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/host/include -DCMAKE_HAVE_LIBC_PTHREAD -rdynamic CMakeFiles/cmTC_36b86.dir/src.c.o -o cmTC_36b86 
CMakeFiles/cmTC_36b86.dir/src.c.o: In function `main':
src.c:(.text.startup+0x13): undefined reference to `pthread_create'
src.c:(.text.startup+0x1d): undefined reference to `pthread_detach'
src.c:(.text.startup+0x27): undefined reference to `pthread_cancel'
src.c:(.text.startup+0x33): undefined reference to `pthread_join'
src.c:(.text.startup+0x3e): undefined reference to `pthread_atfork'
collect2: error: ld returned 1 exit status
gmake[2]: *** [cmTC_36b86] Error 1
gmake[2]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp'
gmake[1]: *** [cmTC_36b86/fast] Error 2
gmake[1]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp'


Source file was:
#include <pthread.h>

void* test_func(void* data)
{
  return data;
}

int main(void)
{
  pthread_t thread;
  pthread_create(&thread, NULL, test_func, NULL);
  pthread_detach(thread);
  pthread_cancel(thread);
  pthread_join(thread, NULL);
  pthread_atfork(NULL, NULL, NULL);
  pthread_exit(NULL);

  return 0;
}

Determining if the function pthread_create exists in the pthreads failed with the following output:
Change Dir: /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/gmake cmTC_1df9e/fast && gmake[1]: Entering directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp'
/usr/bin/gmake  -f CMakeFiles/cmTC_1df9e.dir/build.make CMakeFiles/cmTC_1df9e.dir/build
gmake[2]: Entering directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_1df9e.dir/CheckFunctionExists.c.o
/usr/bin/gcc   -O2 -I/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/host/include -DCHECK_FUNCTION_EXISTS=pthread_create -o CMakeFiles/cmTC_1df9e.dir/CheckFunctionExists.c.o -c /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/host/share/cmake-3.18/Modules/CheckFunctionExists.c
Linking C executable cmTC_1df9e
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_1df9e.dir/link.txt --verbose=1
/usr/bin/gcc -O2 -I/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/host/include -DCHECK_FUNCTION_EXISTS=pthread_create -rdynamic CMakeFiles/cmTC_1df9e.dir/CheckFunctionExists.c.o -o cmTC_1df9e  -lpthreads 
/usr/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
gmake[2]: *** [cmTC_1df9e] Error 1
gmake[2]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp'
gmake[1]: *** [cmTC_1df9e/fast] Error 2
gmake[1]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-1/output-1/build/host-gtest-1.11.0/CMakeFiles/CMakeTmp'