Determining if the include file pthread.h exists failed with the following output:
Change Dir: /home/buildroot/autobuild/run/instance-2/output-1/build/spdlog-1.4.1/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_c628d/fast"
make[1]: Entering directory `/home/buildroot/autobuild/run/instance-2/output-1/build/spdlog-1.4.1/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_c628d.dir/build.make CMakeFiles/cmTC_c628d.dir/build
make[2]: Entering directory `/home/buildroot/autobuild/run/instance-2/output-1/build/spdlog-1.4.1/CMakeFiles/CMakeTmp'
Building CXX object CMakeFiles/cmTC_c628d.dir/CheckIncludeFile.cxx.o
/home/buildroot/autobuild/run/instance-2/output-1/host/bin/arm-linux-g++ --sysroot=/home/buildroot/autobuild/run/instance-2/output-1/host/arm-buildroot-linux-uclibcgnueabihf/sysroot    -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os   -DNDEBUG   -o CMakeFiles/cmTC_c628d.dir/CheckIncludeFile.cxx.o -c /home/buildroot/autobuild/run/instance-2/output-1/build/spdlog-1.4.1/CMakeFiles/CMakeTmp/CheckIncludeFile.cxx
/home/buildroot/autobuild/run/instance-2/output-1/build/spdlog-1.4.1/CMakeFiles/CMakeTmp/CheckIncludeFile.cxx:1:10: fatal error: pthread.h: No such file or directory
 #include <pthread.h>
          ^~~~~~~~~~~
compilation terminated.
make[2]: *** [CMakeFiles/cmTC_c628d.dir/CheckIncludeFile.cxx.o] Error 1
make[2]: Leaving directory `/home/buildroot/autobuild/run/instance-2/output-1/build/spdlog-1.4.1/CMakeFiles/CMakeTmp'
make[1]: *** [cmTC_c628d/fast] Error 2
make[1]: Leaving directory `/home/buildroot/autobuild/run/instance-2/output-1/build/spdlog-1.4.1/CMakeFiles/CMakeTmp'