Determining if the pthread_setname_np exist failed with the following output:
Change Dir: /data/buildroot/buildroot-test/instance-1/output/build/grpc-v1.16.1/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/make cmTC_00b1f/fast 
make[1]: Entering directory '/data/buildroot/buildroot-test/instance-1/output/build/grpc-v1.16.1/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_00b1f.dir/build.make CMakeFiles/cmTC_00b1f.dir/build
make[2]: Entering directory '/data/buildroot/buildroot-test/instance-1/output/build/grpc-v1.16.1/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_00b1f.dir/CheckSymbolExists.c.o
/data/buildroot/buildroot-test/instance-1/output/host/bin/x86_64-linux-gcc --sysroot=/data/buildroot/buildroot-test/instance-1/output/host/x86_64-buildroot-linux-uclibc/sysroot   -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2   -DNDEBUG -fPIE   -o CMakeFiles/cmTC_00b1f.dir/CheckSymbolExists.c.o   -c /data/buildroot/buildroot-test/instance-1/output/build/grpc-v1.16.1/CMakeFiles/CMakeTmp/CheckSymbolExists.c
/data/buildroot/buildroot-test/instance-1/output/build/grpc-v1.16.1/CMakeFiles/CMakeTmp/CheckSymbolExists.c: In function 'main':
/data/buildroot/buildroot-test/instance-1/output/build/grpc-v1.16.1/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8:19: error: 'pthread_setname_np' undeclared (first use in this function); did you mean 'pthread_setcanceltype'?
   return ((int*)(&pthread_setname_np))[argc];
                   ^~~~~~~~~~~~~~~~~~
                   pthread_setcanceltype
/data/buildroot/buildroot-test/instance-1/output/build/grpc-v1.16.1/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8:19: note: each undeclared identifier is reported only once for each function it appears in
make[2]: *** [CMakeFiles/cmTC_00b1f.dir/build.make:66: CMakeFiles/cmTC_00b1f.dir/CheckSymbolExists.c.o] Error 1
make[2]: Leaving directory '/data/buildroot/buildroot-test/instance-1/output/build/grpc-v1.16.1/CMakeFiles/CMakeTmp'
make[1]: *** [Makefile:121: cmTC_00b1f/fast] Error 2
make[1]: Leaving directory '/data/buildroot/buildroot-test/instance-1/output/build/grpc-v1.16.1/CMakeFiles/CMakeTmp'

File /data/buildroot/buildroot-test/instance-1/output/build/grpc-v1.16.1/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
}