Determining if the pthread_create exist failed with the following output:
Change Dir: /tmp/instance-2/output-1/build/pistache-73f248acd6db4c53e6604577b7e13fd5e756f96f/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_29671/fast"
make[1]: Entering directory '/tmp/instance-2/output-1/build/pistache-73f248acd6db4c53e6604577b7e13fd5e756f96f/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_29671.dir/build.make CMakeFiles/cmTC_29671.dir/build
make[2]: Entering directory '/tmp/instance-2/output-1/build/pistache-73f248acd6db4c53e6604577b7e13fd5e756f96f/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_29671.dir/CheckSymbolExists.c.o
/tmp/instance-2/output-1/host/bin/nios2-linux-gcc --sysroot=/tmp/instance-2/output-1/host/nios2-buildroot-linux-gnu/sysroot   -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g2    -o CMakeFiles/cmTC_29671.dir/CheckSymbolExists.c.o   -c /tmp/instance-2/output-1/build/pistache-73f248acd6db4c53e6604577b7e13fd5e756f96f/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTC_29671
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_29671.dir/link.txt --verbose=1
/tmp/instance-2/output-1/host/bin/nios2-linux-gcc --sysroot=/tmp/instance-2/output-1/host/nios2-buildroot-linux-gnu/sysroot -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g2     CMakeFiles/cmTC_29671.dir/CheckSymbolExists.c.o  -o cmTC_29671 
/tmp/instance-2/output-1/host/opt/ext-toolchain/bin/../lib/gcc/nios2-buildroot-linux-gnu/8.3.0/../../../../nios2-buildroot-linux-gnu/bin/ld: CMakeFiles/cmTC_29671.dir/CheckSymbolExists.c.o: in function `main':
/tmp/instance-2/output-1/build/pistache-73f248acd6db4c53e6604577b7e13fd5e756f96f/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8: undefined reference to `pthread_create'
/tmp/instance-2/output-1/host/opt/ext-toolchain/bin/../lib/gcc/nios2-buildroot-linux-gnu/8.3.0/../../../../nios2-buildroot-linux-gnu/bin/ld: /tmp/instance-2/output-1/build/pistache-73f248acd6db4c53e6604577b7e13fd5e756f96f/CMakeFiles/CMakeTmp/CheckSymbolExists.c:8: undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/cmTC_29671.dir/build.make:87: cmTC_29671] Error 1
make[2]: Leaving directory '/tmp/instance-2/output-1/build/pistache-73f248acd6db4c53e6604577b7e13fd5e756f96f/CMakeFiles/CMakeTmp'
make[1]: *** [Makefile:121: cmTC_29671/fast] Error 2
make[1]: Leaving directory '/tmp/instance-2/output-1/build/pistache-73f248acd6db4c53e6604577b7e13fd5e756f96f/CMakeFiles/CMakeTmp'

File /tmp/instance-2/output-1/build/pistache-73f248acd6db4c53e6604577b7e13fd5e756f96f/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
}