Determining if the pthread_create exist failed with the following output:
Change Dir: /home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_a069b/fast"
make[1]: Entering directory `/home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_a069b.dir/build.make CMakeFiles/cmTC_a069b.dir/build
make[2]: Entering directory `/home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_a069b.dir/CheckSymbolExists.c.o
/home/buildroot/autobuild/run/instance-2/output-1/host/bin/aarch64-linux-gnu-gcc --sysroot=/home/buildroot/autobuild/run/instance-2/output-1/host/aarch64-buildroot-linux-gnu/sysroot   -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g2    -o CMakeFiles/cmTC_a069b.dir/CheckSymbolExists.c.o   -c /home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTC_a069b
/home/buildroot/autobuild/run/instance-2/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_a069b.dir/link.txt --verbose=1
/home/buildroot/autobuild/run/instance-2/output-1/host/bin/aarch64-linux-gnu-gcc --sysroot=/home/buildroot/autobuild/run/instance-2/output-1/host/aarch64-buildroot-linux-gnu/sysroot -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g2     -rdynamic CMakeFiles/cmTC_a069b.dir/CheckSymbolExists.c.o  -o cmTC_a069b 
CMakeFiles/cmTC_a069b.dir/CheckSymbolExists.c.o: In function `main':
/home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8: undefined reference to `pthread_create'
/home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8: undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
make[2]: *** [cmTC_a069b] Error 1
make[2]: Leaving directory `/home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp'
make[1]: *** [cmTC_a069b/fast] Error 2
make[1]: Leaving directory `/home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp'

File /home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp/CheckSymbolExists.c:
/* */
#include <pthread.h>

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/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_d36bf/fast"
make[1]: Entering directory `/home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_d36bf.dir/build.make CMakeFiles/cmTC_d36bf.dir/build
make[2]: Entering directory `/home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_d36bf.dir/CheckFunctionExists.c.o
/home/buildroot/autobuild/run/instance-2/output-1/host/bin/aarch64-linux-gnu-gcc --sysroot=/home/buildroot/autobuild/run/instance-2/output-1/host/aarch64-buildroot-linux-gnu/sysroot   -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g2 -DCHECK_FUNCTION_EXISTS=pthread_create   -o CMakeFiles/cmTC_d36bf.dir/CheckFunctionExists.c.o   -c /home/buildroot/autobuild/run/instance-2/output-1/host/share/cmake-3.8/Modules/CheckFunctionExists.c
Linking C executable cmTC_d36bf
/home/buildroot/autobuild/run/instance-2/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_d36bf.dir/link.txt --verbose=1
/home/buildroot/autobuild/run/instance-2/output-1/host/bin/aarch64-linux-gnu-gcc --sysroot=/home/buildroot/autobuild/run/instance-2/output-1/host/aarch64-buildroot-linux-gnu/sysroot -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g2 -DCHECK_FUNCTION_EXISTS=pthread_create    -rdynamic CMakeFiles/cmTC_d36bf.dir/CheckFunctionExists.c.o  -o cmTC_d36bf -lpthreads 
/home/buildroot/autobuild/run/instance-2/output-1/host/opt/ext-toolchain/bin/../lib/gcc/aarch64-linux-gnu/7.3.1/../../../../aarch64-linux-gnu/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
make[2]: *** [cmTC_d36bf] Error 1
make[2]: Leaving directory `/home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp'
make[1]: *** [cmTC_d36bf/fast] Error 2
make[1]: Leaving directory `/home/buildroot/autobuild/run/instance-2/output-1/build/domoticz-0f411f781ae4fb4a82f592d38a3f40578c149533/CMakeFiles/CMakeTmp'