fips-dawn

[WIP] don't use this yet

This makes a locally compiled Google Dawn SDK available to fips projects as a header webgpu/webgpu.h and static libraries webgpu_dawn, webgpu_glfw and webgpu_cpp.

How to use:

1. Add the fips-dawn dependency to the fips.yml file of your project:

---
imports:
  fips-dawn:
    git: https://github.com/fips-libs/fips-dawn

2. Fetch dependencies: ./fips fetch

3. Check if the new fips verb dawn is recognized: ./fips help dawn, you should see:

   fips dawn install
   fips dawn uninstall
       install and manage Google Dawn SDK

4. Install and build the Dawn SDK: ./fips dawn install, this will take a little while.

5. In your toplevel CMakeLists.txt files, before fips_setup(), define the variable USE_DAWN_SDK (if your build targets are not actually using the DAWN SDK it's better to set this to OFF so that no additional library search paths will be added to the project):

       set(USE_DAWN_SDK ON)

6. Use the Dawn SDK headers and libraries in your project:

   In C or C++ code:

   #include <webgpu/webgpu.h>

   As lib dependency in CMakeLists.txt files:

       fips_libs(webgpu_dawn)

   (and optionally also webgpu_glfw and webgpu_cpp)

   A Debug or Release build of the libraries will be automatically selected depending on the cmake build mode.