Determining if the pthread_create exist failed with the following output:
Change Dir: /var/tmp/portage/dev-ros/pcl_ros-1.4.1-r1/work/perception_pcl-1.4.1/pcl_ros-python2_7/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/gmake" "cmTC_b6c3e/fast"
/usr/bin/gmake -f CMakeFiles/cmTC_b6c3e.dir/build.make CMakeFiles/cmTC_b6c3e.dir/build
gmake[1]: Entering directory '/var/tmp/portage/dev-ros/pcl_ros-1.4.1-r1/work/perception_pcl-1.4.1/pcl_ros-python2_7/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_b6c3e.dir/CheckSymbolExists.c.o
/usr/bin/x86_64-pc-linux-gnu-gcc     -DNDEBUG -march=native -O2 -pipe     -o CMakeFiles/cmTC_b6c3e.dir/CheckSymbolExists.c.o -c /var/tmp/portage/dev-ros/pcl_ros-1.4.1-r1/work/perception_pcl-1.4.1/pcl_ros-python2_7/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTC_b6c3e
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_b6c3e.dir/link.txt --verbose=1
/usr/bin/x86_64-pc-linux-gnu-gcc  -march=native -O2 -pipe     -Wl,-O1 -Wl,--as-needed  CMakeFiles/cmTC_b6c3e.dir/CheckSymbolExists.c.o  -o cmTC_b6c3e -rdynamic 
CMakeFiles/cmTC_b6c3e.dir/CheckSymbolExists.c.o: In function `main':
CheckSymbolExists.c:(.text.startup+0x26): undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
gmake[1]: *** [CMakeFiles/cmTC_b6c3e.dir/build.make:98: cmTC_b6c3e] Error 1
gmake[1]: Leaving directory '/var/tmp/portage/dev-ros/pcl_ros-1.4.1-r1/work/perception_pcl-1.4.1/pcl_ros-python2_7/CMakeFiles/CMakeTmp'
gmake: *** [Makefile:126: cmTC_b6c3e/fast] Error 2

File /var/tmp/portage/dev-ros/pcl_ros-1.4.1-r1/work/perception_pcl-1.4.1/pcl_ros-python2_7/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: /var/tmp/portage/dev-ros/pcl_ros-1.4.1-r1/work/perception_pcl-1.4.1/pcl_ros-python2_7/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/gmake" "cmTC_2d1de/fast"
/usr/bin/gmake -f CMakeFiles/cmTC_2d1de.dir/build.make CMakeFiles/cmTC_2d1de.dir/build
gmake[1]: Entering directory '/var/tmp/portage/dev-ros/pcl_ros-1.4.1-r1/work/perception_pcl-1.4.1/pcl_ros-python2_7/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_2d1de.dir/CheckFunctionExists.c.o
/usr/bin/x86_64-pc-linux-gnu-gcc     -DNDEBUG -march=native -O2 -pipe  -DCHECK_FUNCTION_EXISTS=pthread_create   -o CMakeFiles/cmTC_2d1de.dir/CheckFunctionExists.c.o -c /usr/share/cmake/Modules/CheckFunctionExists.c
Linking C executable cmTC_2d1de
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_2d1de.dir/link.txt --verbose=1
/usr/bin/x86_64-pc-linux-gnu-gcc  -march=native -O2 -pipe  -DCHECK_FUNCTION_EXISTS=pthread_create   -Wl,-O1 -Wl,--as-needed  CMakeFiles/cmTC_2d1de.dir/CheckFunctionExists.c.o  -o cmTC_2d1de -rdynamic -lpthreads 
/usr/lib/gcc/x86_64-pc-linux-gnu/5.4.0/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
gmake[1]: *** [CMakeFiles/cmTC_2d1de.dir/build.make:98: cmTC_2d1de] Error 1
gmake[1]: Leaving directory '/var/tmp/portage/dev-ros/pcl_ros-1.4.1-r1/work/perception_pcl-1.4.1/pcl_ros-python2_7/CMakeFiles/CMakeTmp'
gmake: *** [Makefile:126: cmTC_2d1de/fast] Error 2