Determining if the pthread_create exist failed with the following output:
Change Dir: /prog/www/w3/rpki.realmv6.org/html/doxygen/rtrlib-0.3.5/CMakeFiles/CMakeTmp

Run Build Command:/usr/bin/make "cmTryCompileExec4232100747/fast"
/usr/bin/make -f CMakeFiles/cmTryCompileExec4232100747.dir/build.make CMakeFiles/cmTryCompileExec4232100747.dir/build
make[1]: Entering directory `/prog/www/w3/rpki.realmv6.org/html/doxygen/rtrlib-0.3.5/CMakeFiles/CMakeTmp'
/usr/bin/cmake -E cmake_progress_report /prog/www/w3/rpki.realmv6.org/html/doxygen/rtrlib-0.3.5/CMakeFiles/CMakeTmp/CMakeFiles 1
Building C object CMakeFiles/cmTryCompileExec4232100747.dir/CheckSymbolExists.c.o
/usr/bin/cc   -Wall -std=gnu99 -fstack-protector-all    -o CMakeFiles/cmTryCompileExec4232100747.dir/CheckSymbolExists.c.o   -c /prog/www/w3/rpki.realmv6.org/html/doxygen/rtrlib-0.3.5/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTryCompileExec4232100747
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTryCompileExec4232100747.dir/link.txt --verbose=1
/usr/bin/cc   -Wall -std=gnu99 -fstack-protector-all     CMakeFiles/cmTryCompileExec4232100747.dir/CheckSymbolExists.c.o  -o cmTryCompileExec4232100747 -rdynamic 
CMakeFiles/cmTryCompileExec4232100747.dir/CheckSymbolExists.c.o: In function `main':
CheckSymbolExists.c:(.text+0x29): undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
make[1]: *** [cmTryCompileExec4232100747] Error 1
make[1]: Leaving directory `/prog/www/w3/rpki.realmv6.org/html/doxygen/rtrlib-0.3.5/CMakeFiles/CMakeTmp'
make: *** [cmTryCompileExec4232100747/fast] Error 2

File /prog/www/w3/rpki.realmv6.org/html/doxygen/rtrlib-0.3.5/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: /prog/www/w3/rpki.realmv6.org/html/doxygen/rtrlib-0.3.5/CMakeFiles/CMakeTmp

Run Build Command:/usr/bin/make "cmTryCompileExec700449011/fast"
/usr/bin/make -f CMakeFiles/cmTryCompileExec700449011.dir/build.make CMakeFiles/cmTryCompileExec700449011.dir/build
make[1]: Entering directory `/prog/www/w3/rpki.realmv6.org/html/doxygen/rtrlib-0.3.5/CMakeFiles/CMakeTmp'
/usr/bin/cmake -E cmake_progress_report /prog/www/w3/rpki.realmv6.org/html/doxygen/rtrlib-0.3.5/CMakeFiles/CMakeTmp/CMakeFiles 1
Building C object CMakeFiles/cmTryCompileExec700449011.dir/CheckFunctionExists.c.o
/usr/bin/cc   -Wall -std=gnu99 -fstack-protector-all -DCHECK_FUNCTION_EXISTS=pthread_create   -o CMakeFiles/cmTryCompileExec700449011.dir/CheckFunctionExists.c.o   -c /usr/share/cmake-2.8/Modules/CheckFunctionExists.c
Linking C executable cmTryCompileExec700449011
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTryCompileExec700449011.dir/link.txt --verbose=1
/usr/bin/cc   -Wall -std=gnu99 -fstack-protector-all -DCHECK_FUNCTION_EXISTS=pthread_create    CMakeFiles/cmTryCompileExec700449011.dir/CheckFunctionExists.c.o  -o cmTryCompileExec700449011 -rdynamic -lpthreads 
/usr/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
make[1]: *** [cmTryCompileExec700449011] Error 1
make[1]: Leaving directory `/prog/www/w3/rpki.realmv6.org/html/doxygen/rtrlib-0.3.5/CMakeFiles/CMakeTmp'
make: *** [cmTryCompileExec700449011/fast] Error 2