Ubuntu 23.10 build failed: "cpu_user_regs_union_xxxx" is not a valid Ident

[Wenzel]

From #56: https://github.com/Wenzel/xenctrl/actions/runs/7139239177/job/19442221626?pr=56

    Compiling enum-primitive-derive v0.3.0
   Compiling xenvmevent-sys v0.1.3
The following warnings were emitted during compilation:

warning: couldn't execute `llvm-config --prefix` (error: No such file or directory (os error 2))
warning: set the LLVM_CONFIG_PATH environment variable to a valid `llvm-config` executable

error: failed to run custom build command for `xenvmevent-sys v0.1.3`

Caused by:
  process didn't exit successfully: `/__w/xenctrl/xenctrl/target/debug/build/xenvmevent-sys-6fcb983e477eb5d4/build-script-build` (exit status: 101)
  --- stdout
  cargo:warning=couldn't execute `llvm-config --prefix` (error: No such file or directory (os error 2))
  cargo:warning=set the LLVM_CONFIG_PATH environment variable to a valid `llvm-config` executable

  --- stderr
  thread 'main' panicked at /github/home/.cargo/registry/src/index.crates.io-6f17d22bba15001f/bindgen-0.52.0/src/ir/context.rs:893:9:
  "cpu_user_regs_union_(anonymous_at_/usr/include/xen/arch-x86/xen-x86_64_h_163_5)" is not a valid Ident
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...
Error: Process completed with exit code 101.

The build fails due to xenvmevent-sys build script.

Related:

• SO: https://stackoverflow.com/questions/76443280/rust-bindgen-causes-a-is-not-a-valid-ident-error-on-build
• bindgen: thread 'main' panicked at '"__mbstate_t_(anonymous_struct_at_foo_cc_2_3)" is not a valid Ident' rust-lang/rust-bindgen#2312
• libclang change: llvm/llvm-project@19e984e#diff-cde6fae42b53073a85e0901697f60ea80262705f86643b7b27524c7bd24c6f80

[Wenzel]

Possible fix:

• downgrade Clang < 16
• update bindgen >= v0.62.0