Determining if the pthread_create exist failed with the following output:
Change Dir: /users/www/rtrlib.realmv6.org/html/doxygen/rtrlib-github/CMakeFiles/CMakeTmp

Run Build Command:/bin/gmake "cmTryCompileExec3920224552/fast"
/bin/gmake -f CMakeFiles/cmTryCompileExec3920224552.dir/build.make CMakeFiles/cmTryCompileExec3920224552.dir/build
gmake[1]: Entering directory `/users/www/rtrlib.realmv6.org/html/doxygen/rtrlib-github/CMakeFiles/CMakeTmp'
/usr/bin/cmake -E cmake_progress_report /users/www/rtrlib.realmv6.org/html/doxygen/rtrlib-github/CMakeFiles/CMakeTmp/CMakeFiles 1
Building C object CMakeFiles/cmTryCompileExec3920224552.dir/CheckSymbolExists.c.o
/bin/cc   -Wall -std=gnu99 -fstack-protector-all    -o CMakeFiles/cmTryCompileExec3920224552.dir/CheckSymbolExists.c.o   -c /users/www/rtrlib.realmv6.org/html/doxygen/rtrlib-github/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTryCompileExec3920224552
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTryCompileExec3920224552.dir/link.txt --verbose=1
/bin/cc   -Wall -std=gnu99 -fstack-protector-all     CMakeFiles/cmTryCompileExec3920224552.dir/CheckSymbolExists.c.o  -o cmTryCompileExec3920224552 -rdynamic 
CMakeFiles/cmTryCompileExec3920224552.dir/CheckSymbolExists.c.o: In function `main':
CheckSymbolExists.c:(.text+0x29): undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
gmake[1]: Leaving directory `/users/www/rtrlib.realmv6.org/html/doxygen/rtrlib-github/CMakeFiles/CMakeTmp'
gmake[1]: *** [cmTryCompileExec3920224552] Error 1
gmake: *** [cmTryCompileExec3920224552/fast] Error 2

File /users/www/rtrlib.realmv6.org/html/doxygen/rtrlib-github/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: /users/www/rtrlib.realmv6.org/html/doxygen/rtrlib-github/CMakeFiles/CMakeTmp

Run Build Command:/bin/gmake "cmTryCompileExec829164648/fast"
/bin/gmake -f CMakeFiles/cmTryCompileExec829164648.dir/build.make CMakeFiles/cmTryCompileExec829164648.dir/build
gmake[1]: Entering directory `/users/www/rtrlib.realmv6.org/html/doxygen/rtrlib-github/CMakeFiles/CMakeTmp'
/usr/bin/cmake -E cmake_progress_report /users/www/rtrlib.realmv6.org/html/doxygen/rtrlib-github/CMakeFiles/CMakeTmp/CMakeFiles 1
Building C object CMakeFiles/cmTryCompileExec829164648.dir/CheckFunctionExists.c.o
/bin/cc   -Wall -std=gnu99 -fstack-protector-all -DCHECK_FUNCTION_EXISTS=pthread_create   -o CMakeFiles/cmTryCompileExec829164648.dir/CheckFunctionExists.c.o   -c /usr/share/cmake/Modules/CheckFunctionExists.c
Linking C executable cmTryCompileExec829164648
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTryCompileExec829164648.dir/link.txt --verbose=1
/bin/cc   -Wall -std=gnu99 -fstack-protector-all -DCHECK_FUNCTION_EXISTS=pthread_create    CMakeFiles/cmTryCompileExec829164648.dir/CheckFunctionExists.c.o  -o cmTryCompileExec829164648 -rdynamic -lpthreads 
/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
gmake[1]: *** [cmTryCompileExec829164648] Error 1
gmake[1]: Leaving directory `/users/www/rtrlib.realmv6.org/html/doxygen/rtrlib-github/CMakeFiles/CMakeTmp'
gmake: *** [cmTryCompileExec829164648/fast] Error 2