Python 3.* required to build shaderc about ogre-next-deps

[darksylinc]

Would you like this documented?

Yes please! This was brought to my attention some time ago but it was never addressed.

Is "shaderc" necessary for the vulkan renderer?

Short answer:
Sadly yes. Shaderc is a gigantic dependency from which we use little of it but it is needed to get glslang properly working in all platforms.

Long answer:
In theory we shouldn't need it because we only needed glslang (shaderc is a compilation of tools, and includes glslang and a stable C interface to glslang we don't actually use) and I had trouble to link against glslang directly in all the configurations we have (Debug, Release, C++98, C++ >= 11, Android, Linux, Windows) while with shaderc it just worked.

It didn't make any sense, but Google somehow sorted that out.

Without glslang we cannot compile glsl shaders; which is currently the only shader format we support for Vulkan.

[oldmanauz]

@darksylinc, Another issue I just got, all the dependencies build fine in debug/release, but when building the "INSTALL" project:

"/OUT:.....\ogre-next-deps\build\src\shaderc-prefix\src\shaderc-build\libshaderc_util\Debug\shaderc_util.lib" /NOLOGO /MACHINE:X64 /machine:x64 shaderc_util.dir\Debug\args.obj
2>  shaderc_util.dir\Debug\compiler.obj
2>  shaderc_util.dir\Debug\file_finder.obj
2>  shaderc_util.dir\Debug\io.obj
2>  shaderc_util.dir\Debug\message.obj
2>LINK : fatal error LNK1104: cannot open file 'shaderc_util.dir\Debug\message.obj' [...\ogre-next-deps\build\src\shaderc-prefix\src\shaderc-build\libshaderc_util\shaderc_util.vcxproj]
2>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Microsoft\VC\v160\Microsoft.CppCommon.targets(241,5): error MSB8066: Custom build for '...\ogre-next-deps\build\CMakeFiles\d14543c6218fc9f077e713722cf889fe\shaderc-build.rule;...\ogre-next-deps\build\CMakeFiles\d14543c6218fc9f077e713722cf889fe\shaderc-install.rule;...\ogre-next-deps\build\CMakeFiles\b42f6240be198c9ffb646529365d769a\shaderc-complete.rule;...\ogre-next-deps\build\CMakeFiles\f54f24ee0f59ec4d2c4f5236caa1b932\shaderc.rule' exited with code 1.
2>Done building project "shaderc.vcxproj" -- FAILED.

For both debug and release. The debug and release "message.obj" files exist at "...\ogre-next-deps\build\src\shaderc-prefix\src\shaderc-build\libshaderc_util\shaderc_util.dir[Debug|Release]".
Am I doing something stupid?