Determining if the pthread_create exist failed with the following output:
Change Dir: /home/avasile/src/OpenSceneGraph-3.4.0/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/gmake" "cmTryCompileExec4115673882/fast"
/usr/bin/gmake -f CMakeFiles/cmTryCompileExec4115673882.dir/build.make CMakeFiles/cmTryCompileExec4115673882.dir/build
gmake[1]: Entering directory `/home/avasile/src/OpenSceneGraph-3.4.0/CMakeFiles/CMakeTmp'
/usr/local/bin/cmake -E cmake_progress_report /home/avasile/src/OpenSceneGraph-3.4.0/CMakeFiles/CMakeTmp/CMakeFiles 1
Building C object CMakeFiles/cmTryCompileExec4115673882.dir/CheckSymbolExists.c.o
/usr/bin/cc    -o CMakeFiles/cmTryCompileExec4115673882.dir/CheckSymbolExists.c.o   -c /home/avasile/src/OpenSceneGraph-3.4.0/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTryCompileExec4115673882
/usr/local/bin/cmake -E cmake_link_script CMakeFiles/cmTryCompileExec4115673882.dir/link.txt --verbose=1
/usr/bin/cc       CMakeFiles/cmTryCompileExec4115673882.dir/CheckSymbolExists.c.o  -o cmTryCompileExec4115673882 -rdynamic 
CMakeFiles/cmTryCompileExec4115673882.dir/CheckSymbolExists.c.o: In function `main':
CheckSymbolExists.c:(.text+0xc): undefined reference to `pthread_create'
collect2: ld returned 1 exit status
gmake[1]: Leaving directory `/home/avasile/src/OpenSceneGraph-3.4.0/CMakeFiles/CMakeTmp'
gmake[1]: *** [cmTryCompileExec4115673882] Error 1
gmake: *** [cmTryCompileExec4115673882/fast] Error 2

File /home/avasile/src/OpenSceneGraph-3.4.0/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/avasile/src/OpenSceneGraph-3.4.0/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/gmake" "cmTryCompileExec2811812773/fast"
/usr/bin/gmake -f CMakeFiles/cmTryCompileExec2811812773.dir/build.make CMakeFiles/cmTryCompileExec2811812773.dir/build
gmake[1]: Entering directory `/home/avasile/src/OpenSceneGraph-3.4.0/CMakeFiles/CMakeTmp'
/usr/local/bin/cmake -E cmake_progress_report /home/avasile/src/OpenSceneGraph-3.4.0/CMakeFiles/CMakeTmp/CMakeFiles 1
Building C object CMakeFiles/cmTryCompileExec2811812773.dir/CheckFunctionExists.c.o
/usr/bin/cc   -DCHECK_FUNCTION_EXISTS=pthread_create   -o CMakeFiles/cmTryCompileExec2811812773.dir/CheckFunctionExists.c.o   -c /usr/local/share/cmake-3.2/Modules/CheckFunctionExists.c
Linking C executable cmTryCompileExec2811812773
/usr/local/bin/cmake -E cmake_link_script CMakeFiles/cmTryCompileExec2811812773.dir/link.txt --verbose=1
/usr/bin/cc   -DCHECK_FUNCTION_EXISTS=pthread_create    CMakeFiles/cmTryCompileExec2811812773.dir/CheckFunctionExists.c.o  -o cmTryCompileExec2811812773 -rdynamic -lpthreads 
/usr/bin/ld: cannot find -lpthreads
collect2: ld returned 1 exit status
gmake[1]: Leaving directory `/home/avasile/src/OpenSceneGraph-3.4.0/CMakeFiles/CMakeTmp'
gmake[1]: *** [cmTryCompileExec2811812773] Error 1
gmake: *** [cmTryCompileExec2811812773/fast] Error 2