build fails due to bgfx shaderc webgpu dependency

[PinkMushroom]

btw, i don't need webgpu, so a work-around that simply skipped this would be great.

this is on a tree i cloned within last couple of days, and on linux (obviously).

strangely my bgfx installation built without any errors, so it's a bit odd that this dies.

==== Building shaderc (debug64) ====
Creating ../../linux64_gcc/obj/x64/Debug/shaderc
Creating ../../linux64_gcc/obj/x64/Debug/shaderc/bgfx/tools/shaderc
shaderc.cpp
shaderc_glsl.cpp
shaderc_hlsl.cpp
shaderc_metal.cpp
shaderc_pssl.cpp
shaderc_spirv.cpp
../../../../bgfx/tools/shaderc/shaderc_spirv.cpp:17:10: fatal error: webgpu/webgpu_cpp.h: No such file or directory
#include <webgpu/webgpu_cpp.h>
^~~~~~~~~~~~~~~~~~~~~
compilation terminated.
shaderc.make:212: recipe for target '../../linux64_gcc/obj/x64/Debug/shaderc/bgfx/tools/shaderc/shaderc_spirv.o' failed
make[1]: *** [../../linux64_gcc/obj/x64/Debug/shaderc/bgfx/tools/shaderc/shaderc_spirv.o] Error 1
make[1]: *** Waiting for unfinished jobs....
Makefile:96: recipe for target 'shaderc' failed
make: *** [shaderc] Error 2