Dependency `sys/sysctl.h` is deprecated

[chrisdonlan]

Running into issues building these samples on Fedora 33. Specifically, the threaded rendering example.

The following file is deprecated from glibc,

sys/sysctl.h

sysctl is deprecated

Error output:

make[3]: Entering directory '/home/chris/ray-tracing/build'
[ 16%] Building CXX object gl_vk_bk3dthreaded/CMakeFiles/gl_vk_bk3dthreaded.dir/mt/CThread.cpp.o
/home/chris/ray-tracing/gl_vk_bk3dthreaded/mt/CThread.cpp:34:13: fatal error: sys/sysctl.h: No such file or directory
   34 | #   include <sys/sysctl.h>
      |             ^~~~~~~~~~~~~~
compilation terminated.
make[3]: *** [gl_vk_bk3dthreaded/CMakeFiles/gl_vk_bk3dthreaded.dir/build.make:173: gl_vk_bk3dthreaded/CMakeFiles/gl_vk_bk3dthreaded.dir/mt/CThread.cpp.o] Error 1
make[3]: Leaving directory '/home/chris/lab/ray-tracing/build'

[chrisdonlan]

The versions of glib available on Fedora @ release 33:

[chris@localhost ray-tracing]$ dnf --showduplicates list glibc-devel
AMDGPU Packages
Fedora Modular 33 - x86_64 - Updates
Fedora 33 - x86_64 - Updates
Fedora 33 - x86_64 - Updates

Installed Packages
glibc-devel.x86_64  2.32-1.fc33  @fedora

Available Packages
glibc-devel.i686  2.32-1.fc33  fedora 
glibc-devel.x86_64  2.32-1.fc33  fedora 
glibc-devel.i686  2.32-3.fc33  updates
glibc-devel.x86_64  2.32-3.fc33  updates

What I did to move forward with the build:

I removed line 34 from mt/CThread.cpp, here

However, I then had to make an additional change.

I do not know the optimal spot to place this information, so I added the library links -lpthread -lm to the following positions in the CMakeLists.txt of the same project:

here

and here