Performing C++ SOURCE FILE Test CMAKE_HAVE_LIBC_PTHREAD failed with the following output:
Change Dir: /home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/make cmTC_2f164/fast && make[1]: Entering directory '/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_2f164.dir/build.make CMakeFiles/cmTC_2f164.dir/build
make[2]: Entering directory '/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp'
Building CXX object CMakeFiles/cmTC_2f164.dir/src.cxx.o
/home/buildroot/autobuild/instance-1/output-1/host/bin/arm-linux-g++ --sysroot=/home/buildroot/autobuild/instance-1/output-1/host/arm-buildroot-uclinux-uclibcgnueabi/sysroot    -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -Wl,-elf2flt -static -Wl,-elf2flt -static -DCMAKE_HAVE_LIBC_PTHREAD  -DNDEBUG   -o CMakeFiles/cmTC_2f164.dir/src.cxx.o -c /home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp/src.cxx
/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp/src.cxx: In function 'int main()':
/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp/src.cxx:14:3: error: 'pthread_atfork' was not declared in this scope
   pthread_atfork(NULL, NULL, NULL);
   ^~~~~~~~~~~~~~
/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp/src.cxx:14:3: note: suggested alternative: 'pthread_attr_t'
   pthread_atfork(NULL, NULL, NULL);
   ^~~~~~~~~~~~~~
   pthread_attr_t
CMakeFiles/cmTC_2f164.dir/build.make:65: recipe for target 'CMakeFiles/cmTC_2f164.dir/src.cxx.o' failed
make[2]: *** [CMakeFiles/cmTC_2f164.dir/src.cxx.o] Error 1
make[2]: Leaving directory '/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp'
Makefile:121: recipe for target 'cmTC_2f164/fast' failed
make[1]: *** [cmTC_2f164/fast] Error 2
make[1]: Leaving directory '/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/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: /home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/make cmTC_da08b/fast && make[1]: Entering directory '/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_da08b.dir/build.make CMakeFiles/cmTC_da08b.dir/build
make[2]: Entering directory '/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp'
Building CXX object CMakeFiles/cmTC_da08b.dir/CheckFunctionExists.cxx.o
/home/buildroot/autobuild/instance-1/output-1/host/bin/arm-linux-g++ --sysroot=/home/buildroot/autobuild/instance-1/output-1/host/arm-buildroot-uclinux-uclibcgnueabi/sysroot    -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -Wl,-elf2flt -static -Wl,-elf2flt -static -DCHECK_FUNCTION_EXISTS=pthread_create  -DNDEBUG   -o CMakeFiles/cmTC_da08b.dir/CheckFunctionExists.cxx.o -c /home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CheckLibraryExists/CheckFunctionExists.cxx
Linking CXX executable cmTC_da08b
/home/buildroot/autobuild/instance-1/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_da08b.dir/link.txt --verbose=1
/home/buildroot/autobuild/instance-1/output-1/host/bin/arm-linux-g++ --sysroot=/home/buildroot/autobuild/instance-1/output-1/host/arm-buildroot-uclinux-uclibcgnueabi/sysroot  -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -Wl,-elf2flt -static -Wl,-elf2flt -static -DCHECK_FUNCTION_EXISTS=pthread_create  -DNDEBUG  -Wl,-elf2flt -static  CMakeFiles/cmTC_da08b.dir/CheckFunctionExists.cxx.o  -o cmTC_da08b -lpthreads 
/home/buildroot/autobuild/instance-1/output-1/host/opt/ext-toolchain/arm-buildroot-uclinux-uclibcgnueabi/bin/ld.real: cannot find -lpthreads
collect2: error: ld returned 1 exit status
CMakeFiles/cmTC_da08b.dir/build.make:86: recipe for target 'cmTC_da08b' failed
make[2]: *** [cmTC_da08b] Error 1
make[2]: Leaving directory '/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp'
Makefile:121: recipe for target 'cmTC_da08b/fast' failed
make[1]: *** [cmTC_da08b/fast] Error 2
make[1]: Leaving directory '/home/buildroot/autobuild/instance-1/output-1/build/spdlog-1.4.2/CMakeFiles/CMakeTmp'