Red Bear OS — microkernel OS in Rust, based on Redox

Derivative of Redox OS (https://www.redox-os.org) adding:
- AMD GPU driver (amdgpu) via LinuxKPI compat layer
- ext4 filesystem support (ext4d scheme daemon)
- ACPI fixes for AMD bare metal (x2APIC, DMAR, IVRS, MCFG)
- Custom branding (hostname, os-release, boot identity)

Build system is full upstream Redox with RBOS overlay in local/.
Patches for kernel, base, and relibc are symlinked from local/patches/
and protected from make clean/distclean. Custom recipes live in
local/recipes/ with symlinks into the recipes/ search path.

Build:  make all CONFIG_NAME=redbear-full
Sync:   ./local/scripts/sync-upstream.sh

recipes/dev/clang21/recipe.toml

@@ -0,0 +1,90 @@
+[source]
+same_as = "../llvm21"
+
+[build]
+template = "custom"
+dependencies = [
+    "llvm21",
+]
+dev-dependencies = [
+    "libstdcxx", # no idea
+    "llvm21.dev",
+    "llvm21.runtime",
+    "host:xz",
+    "host:libarchive",  # workaround for cmake error
+]
+script = """
+DYNAMIC_INIT
+ARCH="$(echo "${TARGET}" | cut -d - -f1)"
+
+generate_cookbook_cmake_file "$COOKBOOK_HOST_TARGET" "" "$COOKBOOK_TOOLCHAIN" native.cmake
+
+COOKBOOK_CMAKE_FLAGS+=(
+    -DLLVM_ROOT="${COOKBOOK_SYSROOT}"
+    -DCLANG_LINK_CLANG_DYLIB=ON
+    -DLIBCLANG_BUILD_STATIC=1
+    -DLLVM_BUILD_UTILS=On
+
+# the shared options from llvm
+    -DCMAKE_CXX_FLAGS="--std=gnu++11"
+    -DBUILD_SHARED_LIBS=False
+    -DLLVM_BUILD_EXAMPLES=Off
+    -DLLVM_BUILD_TESTS=Off
+    -DLLVM_DEFAULT_TARGET_TRIPLE="${TARGET}"
+    -DLLVM_ENABLE_LTO=Off
+    -DLLVM_ENABLE_RTTI=On
+    -DLLVM_ENABLE_THREADS=On
+    -DLLVM_INCLUDE_EXAMPLES=Off
+    -DLLVM_INCLUDE_TESTS=Off
+    -DLLVM_OPTIMIZED_TABLEGEN=On
+    -DLLVM_TARGET_ARCH=$ARCH
+    -DLLVM_TOOLS_INSTALL_DIR=bin
+    -DLLVM_UTILS_INSTALL_DIR=bin
+    -DUNIX=1
+)
+
+COOKBOOK_SOURCE="$COOKBOOK_SOURCE/clang"
+
+if [ "$TARGET" = "$COOKBOOK_HOST_TARGET" ]; then
+
+    COOKBOOK_CMAKE_FLAGS+=( -DLLVM_TABLEGEN_EXE=${COOKBOOK_TOOLCHAIN}/bin/llvm-tblgen )
+
+    "${COOKBOOK_CMAKE}" "${COOKBOOK_SOURCE}" \
+        -DCMAKE_BUILD_TYPE=Release \
+        -DCMAKE_INSTALL_INCLUDEDIR=include \
+        -DCMAKE_INSTALL_LIBDIR=lib \
+        -DCMAKE_INSTALL_OLDINCLUDEDIR=/include \
+        -DCMAKE_INSTALL_PREFIX=/usr \
+        -DCMAKE_INSTALL_SBINDIR=bin \
+        -DCMAKE_TOOLCHAIN_FILE=native.cmake \
+        -GNinja \
+        -Wno-dev \
+        "${COOKBOOK_CMAKE_FLAGS[@]}" \
+        "$@"
+
+    # All distros use clever tricks to this problem. I have no idea how I came up with this
+    export PATH="$PATH:$COOKBOOK_STAGE/usr/bin"
+    DESTDIR="${COOKBOOK_STAGE}" "${COOKBOOK_NINJA}" install-clang-tblgen
+    "${COOKBOOK_NINJA}" -j"${COOKBOOK_MAKE_JOBS}"
+    DESTDIR="${COOKBOOK_STAGE}" "${COOKBOOK_NINJA}" install -j"${COOKBOOK_MAKE_JOBS}"
+
+else
+
+    COOKBOOK_CMAKE_FLAGS+=(
+        -DCROSS_TOOLCHAIN_FLAGS_NATIVE="-DCMAKE_TOOLCHAIN_FILE=$(realpath native.cmake)"
+        -DCLANG_TABLEGEN_EXE=${COOKBOOK_HOST_SYSROOT}/bin/clang-tblgen
+        -DLLVM_TABLEGEN_EXE=${COOKBOOK_HOST_SYSROOT}/bin/llvm-tblgen
+    )
+    cookbook_cmake
+
+fi
+
+"""
+
+[[optional-packages]]
+name = "dev"
+files = [
+    "usr/include/clang*/**",
+    "usr/lib/libclang*.a",
+    "usr/lib/cmake/clang/**",
+]