Conformance test doesn't run with CMake 4

[jschwe]

CMake 4 removed compatibility with CMake < 3.5, resulting in the following error when building the woff2 tools:

CMake Error at CMakeLists.txt:10 (cmake_minimum_required):
  Compatibility with CMake < 3.5 has been removed from CMake.

  Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
  to tell CMake that the project requires at least <min> but has been updated
  to work with policies introduced by <max> or earlier.

  Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway.

[nicoburns]

Hmm... I guess we could apply google/woff2#187 locally. Although it would be ideal if this was fixed upstream!

Or I guess we could copy the fontsan code and build with a build.rs rather than CMAKE?