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-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/gmake cmTC_b174e/fast && gmake[1]: Entering directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp'
/usr/bin/gmake -f CMakeFiles/cmTC_b174e.dir/build.make CMakeFiles/cmTC_b174e.dir/build
gmake[2]: Entering directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_b174e.dir/src.c.o
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/bin/aarch64-none-linux-gnu-gcc --sysroot=/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/aarch64-buildroot-linux-gnu/sysroot   -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g2 -std=gnu99 -Wall -Wextra -D__FILENAME__='"CMakeFiles/CMakeTmp/src.c"' -DCMAKE_HAVE_LIBC_PTHREAD   -o CMakeFiles/cmTC_b174e.dir/src.c.o   -c /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp/src.c
Linking C executable cmTC_b174e
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_b174e.dir/link.txt --verbose=1
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/bin/aarch64-none-linux-gnu-gcc --sysroot=/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/aarch64-buildroot-linux-gnu/sysroot -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g2 -std=gnu99 -Wall -Wextra -D__FILENAME__='"$(subst /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/,,$(abspath $<))"' -DCMAKE_HAVE_LIBC_PTHREAD    CMakeFiles/cmTC_b174e.dir/src.c.o  -o cmTC_b174e 
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/opt/ext-toolchain/bin/../lib/gcc/aarch64-none-linux-gnu/10.2.1/../../../../aarch64-none-linux-gnu/bin/ld: CMakeFiles/cmTC_b174e.dir/src.c.o: in function `main':
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp/src.c:11: undefined reference to `pthread_create'
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/opt/ext-toolchain/bin/../lib/gcc/aarch64-none-linux-gnu/10.2.1/../../../../aarch64-none-linux-gnu/bin/ld: /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp/src.c:12: undefined reference to `pthread_detach'
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/opt/ext-toolchain/bin/../lib/gcc/aarch64-none-linux-gnu/10.2.1/../../../../aarch64-none-linux-gnu/bin/ld: /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp/src.c:13: undefined reference to `pthread_join'
collect2: error: ld returned 1 exit status
gmake[2]: *** [cmTC_b174e] Error 1
gmake[2]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp'
gmake[1]: *** [cmTC_b174e/fast] Error 2
gmake[1]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/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_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-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/gmake cmTC_19369/fast && gmake[1]: Entering directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp'
/usr/bin/gmake -f CMakeFiles/cmTC_19369.dir/build.make CMakeFiles/cmTC_19369.dir/build
gmake[2]: Entering directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_19369.dir/CheckFunctionExists.c.o
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/bin/aarch64-none-linux-gnu-gcc --sysroot=/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/aarch64-buildroot-linux-gnu/sysroot   -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g2 -std=gnu99 -Wall -Wextra -D__FILENAME__='"/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/share/cmake-3.15/Modules/CheckFunctionExists.c"' -DCHECK_FUNCTION_EXISTS=pthread_create   -o CMakeFiles/cmTC_19369.dir/CheckFunctionExists.c.o   -c /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/share/cmake-3.15/Modules/CheckFunctionExists.c
Linking C executable cmTC_19369
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_19369.dir/link.txt --verbose=1
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/bin/aarch64-none-linux-gnu-gcc --sysroot=/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/aarch64-buildroot-linux-gnu/sysroot -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g2 -std=gnu99 -Wall -Wextra -D__FILENAME__='"$(subst /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/,,$(abspath $<))"' -DCHECK_FUNCTION_EXISTS=pthread_create    CMakeFiles/cmTC_19369.dir/CheckFunctionExists.c.o  -o cmTC_19369 -lpthreads 
/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/host/opt/ext-toolchain/bin/../lib/gcc/aarch64-none-linux-gnu/10.2.1/../../../../aarch64-none-linux-gnu/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
gmake[2]: *** [cmTC_19369] Error 1
gmake[2]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp'
gmake[1]: *** [cmTC_19369/fast] Error 2
gmake[1]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-2/output-1/build/monkey-1.6.9/CMakeFiles/CMakeTmp'