sync code with last improvements from OpenBSD

lib/mesa/docs/rusticl.rst

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+Rusticl
+=======
+
+To build Rusticl you need to satisfy the following build dependencies:
+
+-  ``rustc``
+-  ``rustfmt`` (highly recommended, but only *required* for CI builds
+   or when authoring patches)
+-  ``bindgen``
+-  `LLVM <https://github.com/llvm/llvm-project/>`__ built with
+   ``libclc`` and ``-DLLVM_ENABLE_DUMP=ON``.
+-  `SPIRV-Tools <https://github.com/KhronosGroup/SPIRV-Tools>`__
+-  `SPIRV-LLVM-Translator
+   <https://github.com/KhronosGroup/SPIRV-LLVM-Translator>`__ for a
+   ``libLLVMSPIRVLib.so`` matching your version of LLVM, i.e. if you're
+   using LLVM 15 (``libLLVM.so.15``), then you need a
+   ``libLLVMSPIRVLib.so.15``.
+
+The minimum versions to build Rusticl are:
+
+-  Rust: 1.59
+-  Meson: 0.61.4
+-  Bindgen: 0.58.0
+-  LLVM: 11.0.0 (recommended: 15.0.0)
+-  SPIRV-Tools: any version (recommended: v2022.3)
+
+Afterwards you only need to add ``-Dgallium-rusticl=true -Dllvm=enabled
+-Drust_std=2021`` to your build options.
+
+Most of the code related to Mesa's C code lives inside ``/mesa``, with
+the occasional use of enums, structs or constants through the code base.
+
+If you need help ping ``karolherbst`` either in ``#dri-devel`` or
+``#rusticl`` on OFTC.
+
+Also, make sure that before submitting code to verify the formatting is
+in order. That can easily be done via ``git ls-files */{lib,app}.rs
+| xargs rustfmt``
+
+When submitting Merge Requests or filing bugs related to Rusticl, make
+sure to add the ``Rusticl`` label so people subscribed to that Label get
+pinged.
+
+Known issues
+------------
+
+One issue you might come across is, that the Rust edition meson sets is
+not right. This is a known `meson bug
+<https://github.com/mesonbuild/meson/issues/10664>`__ and in order to
+fix it, simply run ``meson configure $your_build_dir -Drust_std=2021``