* Fixed compile on OpenBSD

* Changed to not use seperate UNIX for cmake

* OpenGLES 2.0 support on PLATFORM_DESKTOP

* exmples raylib_opengl_interop desktop GLES2 support

* rename gles2.h -> glad_gles2.h

Use GLVND also when legacy implementations exist for old cmake versions
<= 3.10. This is a breaking change for old cmake versions (prior to
around 2017-10-05) which will now use GLVND rather than defaulting to
libGL.

This fixes the following warning when building:

    CMake Warning (dev) at /gnu/store/qv13zgbmyx0vjav8iiqp772kp6rxvwnd-cmake-3.24.2/share/cmake-3.24/Modules/FindOpenGL.cmake:315 (message):
      Policy CMP0072 is not set: FindOpenGL prefers GLVND by default when
      available.  Run "cmake --help-policy CMP0072" for policy details.  Use the
      cmake_policy command to set the policy and suppress this warning.

      FindOpenGL found both a legacy GL library:

        OPENGL_gl_LIBRARY: /home/simendsjo/.guix-profile/lib/libGL.so

      and GLVND libraries for OpenGL and GLX:

        OPENGL_opengl_LIBRARY: /home/simendsjo/.guix-profile/lib/libOpenGL.so
        OPENGL_glx_LIBRARY: /home/simendsjo/.guix-profile/lib/libGLX.so

      OpenGL_GL_PREFERENCE has not been set to "GLVND" or "LEGACY", so for
      compatibility with CMake 3.10 and below the legacy GL library will be used.
    Call Stack (most recent call first):
      cmake/LibraryConfigurations.cmake:21 (find_package)
      src/CMakeLists.txt:46 (include)
    This warning is for project developers.  Use -Wno-dev to suppress it.

See https://cmake.org/cmake/help/latest/policy/CMP0072.html

Closes #2825

`android_native_app_glue.c` wasn't appended to the `raylib_sources` as other libraries were.

Co-authored-by: Patrick Martin <martinpatrick@google.com>

* Fixed Compiling Raylib for android Using cmake

* improved the cmake config for android so it don't conflict

* improved the cmake config for android so it don't conflict

* Add find opengl for widnows too.

* Also fix set LIBS_PRIVATE to bi similar to linux and apple targets

* Log a warning if chdir failed, use agnostic CHDIR instead of chdir

* Only include libdrm directory explicitly when not cross compiling

* Documenting the compiler flags

* Moved some android compiler flags and added documentation on them too.

* Some more restructuring.

Removed unnecessary comments that were self described by the code.
Added some more explanations around certain parts of CMake and especially around compiler flags.

CMake relied on this file for configurations and also was interfering in the regular config.h by having a separate definition if building with CMake. This was not entirely correct so instead we will define compile time definitions separately through CMake (CompileDefinitions.cmake) and also will use the provided EXTERNAL_CONFIG_FLAGS that I found that will not use config.h in through the build process.

I also introduced a new compiler option (CUSTOMIZE_BUILD) that when OFF will use the default config.h and when ON will show other options for redefining your own options.

Fixed an error in rlgl.h where if you have both RLGL_STANDALONE and SUPPORT_VR_SIMULATOR you get a compile time error.

* Delete emscripten.cmake

This file is not needed at this point. EMSDK provides a toolchain file that has a lot more things in it and is better supported. Project currently works fine with the documentation provided in Emscripten SDK on how to build projects.

* First pass file separation.

The main two files are cleaner now. Only important things can be seen. Major changes include:
- raylib_static is now the alias instead of raylib
- Repeating segments are removed and pulled into separate files into <root>/cmake
- File is reordered to make more sense
- Installs are better structured
- Library is build into an output directory "raylib" instead of "src"
- All public header files are now set as a public header file
- Source files need to be listed (it is a bad practice to capture them using wildcards and file globs)
- CMakeLists are better commented

* Second pass on the example dirs.

They are quite complex so I'm more hesitant to do major changes. Also it works pretty well. Noticed that I forgot one of the seperated files and added it into src/CMakeLists.txt.

* Returned the header copy as it was convenient to have the public headers copied.

* A better description to the variable RAYLIB_IS_MAIN

Co-authored-by: Rob Loach <robloach@gmail.com>

* Remove debug message

Co-authored-by: Rob Loach <robloach@gmail.com>

* Improvements based on review.

* Simplify the install condition to not be platform specific as it was before.

Co-authored-by: Alexander Neumann <30894796+Neumann-A@users.noreply.github.com>

* Remove some CMAKE variables as they don't affect the build in any way

Co-authored-by: Alexander Neumann <30894796+Neumann-A@users.noreply.github.com>

Co-authored-by: Rob Loach <robloach@gmail.com>
Co-authored-by: Alexander Neumann <30894796+Neumann-A@users.noreply.github.com>