Determining if the pthread_setname_np exist failed with the following output:
Change Dir: /home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_ba18c/fast"
make[1]: Entering directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_ba18c.dir/build.make CMakeFiles/cmTC_ba18c.dir/build
make[2]: Entering directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_ba18c.dir/CheckSymbolExists.c.o
/usr/bin/gcc   -O2 -I/home/buildroot/autobuild/run/instance-3/output-1/host/include  -fPIE   -o CMakeFiles/cmTC_ba18c.dir/CheckSymbolExists.c.o   -c /home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp/CheckSymbolExists.c
/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp/CheckSymbolExists.c: In function 'main':
/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8:19: error: 'pthread_setname_np' undeclared (first use in this function)
   return ((int*)(&pthread_setname_np))[argc];
                   ^
/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8:19: note: each undeclared identifier is reported only once for each function it appears in
make[2]: *** [CMakeFiles/cmTC_ba18c.dir/CheckSymbolExists.c.o] Error 1
make[2]: Leaving directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'
make[1]: *** [cmTC_ba18c/fast] Error 2
make[1]: Leaving directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'

File /home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp/CheckSymbolExists.c:
/* */
#include <pthread.h>

int main(int argc, char** argv)
{
  (void)argv;
#ifndef pthread_setname_np
  return ((int*)(&pthread_setname_np))[argc];
#else
  (void)argc;
  return 0;
#endif
}

Determining if the pthread_create exist failed with the following output:
Change Dir: /home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_5fba5/fast"
make[1]: Entering directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_5fba5.dir/build.make CMakeFiles/cmTC_5fba5.dir/build
make[2]: Entering directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_5fba5.dir/CheckSymbolExists.c.o
/usr/bin/gcc   -O2 -I/home/buildroot/autobuild/run/instance-3/output-1/host/include  -fPIE   -o CMakeFiles/cmTC_5fba5.dir/CheckSymbolExists.c.o   -c /home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTC_5fba5
/home/buildroot/autobuild/run/instance-3/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_5fba5.dir/link.txt --verbose=1
/usr/bin/gcc -O2 -I/home/buildroot/autobuild/run/instance-3/output-1/host/include   -L/home/buildroot/autobuild/run/instance-3/output-1/host/lib -Wl,-rpath,/home/buildroot/autobuild/run/instance-3/output-1/host/lib  CMakeFiles/cmTC_5fba5.dir/CheckSymbolExists.c.o  -o cmTC_5fba5 
CMakeFiles/cmTC_5fba5.dir/CheckSymbolExists.c.o: In function `main':
CheckSymbolExists.c:(.text.startup+0x3): undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
make[2]: *** [cmTC_5fba5] Error 1
make[2]: Leaving directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'
make[1]: *** [cmTC_5fba5/fast] Error 2
make[1]: Leaving directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'

File /home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/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-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_e8d7c/fast"
make[1]: Entering directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_e8d7c.dir/build.make CMakeFiles/cmTC_e8d7c.dir/build
make[2]: Entering directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_e8d7c.dir/CheckFunctionExists.c.o
/usr/bin/gcc   -O2 -I/home/buildroot/autobuild/run/instance-3/output-1/host/include -DCHECK_FUNCTION_EXISTS=pthread_create -fPIE   -o CMakeFiles/cmTC_e8d7c.dir/CheckFunctionExists.c.o   -c /home/buildroot/autobuild/run/instance-3/output-1/host/share/cmake-3.9/Modules/CheckFunctionExists.c
Linking C executable cmTC_e8d7c
/home/buildroot/autobuild/run/instance-3/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_e8d7c.dir/link.txt --verbose=1
/usr/bin/gcc -O2 -I/home/buildroot/autobuild/run/instance-3/output-1/host/include -DCHECK_FUNCTION_EXISTS=pthread_create  -L/home/buildroot/autobuild/run/instance-3/output-1/host/lib -Wl,-rpath,/home/buildroot/autobuild/run/instance-3/output-1/host/lib  CMakeFiles/cmTC_e8d7c.dir/CheckFunctionExists.c.o  -o cmTC_e8d7c -lpthreads 
/usr/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
make[2]: *** [cmTC_e8d7c] Error 1
make[2]: Leaving directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'
make[1]: *** [cmTC_e8d7c/fast] Error 2
make[1]: Leaving directory `/home/buildroot/autobuild/run/instance-3/output-1/build/host-grpc-1.23.0/CMakeFiles/CMakeTmp'