Bundle bindgen-cli from source for Rocky 9.6 builds

The bindgen tool required for kernel Rust support is not packaged in
Rocky Linux 9.6. Replace the bindgen BuildRequires with a bundled
bindgen-cli crate built from vendored source during the RPM build.

Add bundle_bindgen.sh helper script to download, vendor, and tar the
bindgen-cli source for inclusion as Source5000.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Jonathan Dieter <jdieter@ciq.com>

Author: jdieter

ciq/SOURCES/bundle_bindgen.sh

@@ -0,0 +1,39 @@
+#!/bin/sh
+
+# Bundle the bindgen-cli source code to be included in the kernel build.
+# https://crates.io/crates/bindgen-cli
+#
+# The bindgen tool, required to build Rust code in the Linux kernel, is
+# currently only packaged in Fedora/ELN. In order to build CLK kernels
+# on Rocky Linux we need to build bindgen as part of the kernel build.
+
+SOURCES=$1
+
+BINDGEN_CLI=bindgen-cli
+BINDGEN_CLI_VERSION="0.71.1"
+BINDGEN_CLI_CRATE=bindgen-cli.crate
+CRATESIO_API_ENDPOINT=https://crates.io/api/v1/crates/bindgen-cli/${BINDGEN_CLI_VERSION}/download
+
+curl -sL $CRATESIO_API_ENDPOINT -o $SOURCES/$BINDGEN_CLI_CRATE
+tar -xf $SOURCES/$BINDGEN_CLI_CRATE -C $SOURCES
+mv $SOURCES/$BINDGEN_CLI-$BINDGEN_CLI_VERSION $SOURCES/$BINDGEN_CLI
+
+# vendor bindgen-cli
+cd $SOURCES/$BINDGEN_CLI
+mkdir .cargo
+cat > .cargo/config.toml <<EOF
+[source.crates-io]
+replace-with = "vendored-sources"
+
+[source.vendored-sources]
+directory = "vendor"
+EOF
+
+cargo vendor --locked --quiet
+
+cd ..
+tar czf $BINDGEN_CLI.tar.gz $BINDGEN_CLI
+
+# clean up
+rm -f $SOURCES/$BINDGEN_CLI_CRATE
+rm -rf $SOURCES/$BINDGEN_CLI

ciq/SPECS/kernel-clk6.18.spec

@@ -715,7 +715,7 @@ BuildRequires: bzip2, xz, findutils, m4, perl-interpreter, perl-Carp, perl-devel
 BuildRequires: zstd
 %endif
 BuildRequires: gcc, binutils, redhat-rpm-config, hmaccalc, bison, flex, gcc-c++
-BuildRequires: rust, rust-src, bindgen, rustfmt, clippy
+BuildRequires: rust, rust-src, rustfmt, clippy
 BuildRequires: net-tools, hostname, bc, elfutils-devel
 BuildRequires: dwarves
 BuildRequires: python3
@@ -1134,6 +1134,9 @@ Source3002: Patchlist.changelog
 
 Source4000: README.rst
 
+# Bundled bindgen-cli source (not packaged in Rocky 9.6)
+Source5000: bindgen-cli.tar.gz
+
 ## Patches needed for building this package
 
 %if !%{nopatches}
@@ -2238,6 +2241,18 @@ cp_vmlinux()
 %define build_hostldflags %{?build_ldflags}
 %endif
 
+# Build bundled bindgen and add to PATH
+%{log_msg "Build bindgen"}
+BINDGEN_DIR=$RPM_BUILD_ROOT/bindgen
+BINDGEN_BUNDLE_NAME=$(basename %{SOURCE5000} .tar.gz)
+mkdir -p $BINDGEN_DIR
+tar -xf %{SOURCE5000} -C $BINDGEN_DIR
+pushd $BINDGEN_DIR/$BINDGEN_BUNDLE_NAME
+cargo build --offline --frozen --release
+export PATH="$PWD/target/release:$PATH"
+popd
+bindgen --version
+
 %define make %{__make} %{?cross_opts} %{?make_opts} HOSTCFLAGS="%{?build_hostcflags}" HOSTLDFLAGS="%{?build_hostldflags}"
 
 InitBuildVars() {