Fix packaging errors due to modifying outside of OUT_DIR

[alexgeek]

Tried to package but got this:

cargo package
   Packaging openvr_sys v2.1.0 (D:\liv\rust-openvr-sys-og)
    Updating crates.io index
    Packaged 51 files, 1.9MiB (364.3KiB compressed)
   Verifying openvr_sys v2.1.0 (D:\liv\rust-openvr-sys-og)
   Compiling proc-macro2 v1.0.93
   Compiling windows_x86_64_msvc v0.52.6
   Compiling unicode-ident v1.0.16
   Compiling glob v0.3.2
   Compiling prettyplease v0.2.29
   Compiling libc v0.2.169
   Compiling memchr v2.7.4
   Compiling minimal-lexical v0.2.1
   Compiling shlex v1.3.0
   Compiling regex-syntax v0.8.5
   Compiling either v1.13.0
   Compiling bindgen v0.71.1
   Compiling log v0.4.25
   Compiling rustc-hash v2.1.0
   Compiling bitflags v2.8.0
   Compiling cc v1.2.10
   Compiling itertools v0.13.0
   Compiling clang-sys v1.8.1
   Compiling nom v7.1.3
   Compiling windows-targets v0.52.6
   Compiling libloading v0.8.6
   Compiling cmake v0.1.53
   Compiling regex-automata v0.4.9
   Compiling quote v1.0.38
   Compiling syn v2.0.96
   Compiling cexpr v0.6.0
   Compiling regex v1.11.1
   Compiling openvr_sys v2.1.0 (D:\liv\rust-openvr-sys-og\target\package\openvr_sys-2.1.0)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 14.31s
error: failed to verify package tarball

Caused by:
  Source directory was modified by build.rs during cargo publish. Build scripts should not modify anything outside of OUT_DIR.
  Added: D:\liv\rust-openvr-sys-og\target\package\openvr_sys-2.1.0\bindings.rs
        D:\liv\rust-openvr-sys-og\target\package\openvr_sys-2.1.0\openvr\bin
        D:\liv\rust-openvr-sys-og\target\package\openvr_sys-2.1.0\openvr\bin\win64
        D:\liv\rust-openvr-sys-og\target\package\openvr_sys-2.1.0\openvr\bin\win64\Debug
        D:\liv\rust-openvr-sys-og\target\package\openvr_sys-2.1.0\openvr\bin\win64\Debug\openvr_api64.lib

  To proceed despite this, pass the `--no-verify` flag.

Now bindings and CMake is all generated into OUT_DIR and cargo package succeeds, I can publish after this is squashed into master.

[Tsuguri]

Makes sense to build to out_dir. Built locally for me.

One thing: you don't have to bump the version since nothing was released :)