chore: add archive-sparse-checkout.sh (#122)

It is a script to do sparse checkout of btfhub-archive repository.

It can be used like this:

ARCH=x86_64 ./tools/archive-sparse-checkout.sh
ARCH=arm64 DISTRO=ubuntu VERSION=20.04 ./tools/archive-sparse-checkout.sh

tools/archive-sparse-checkout.sh

@@ -0,0 +1,56 @@
+#!/bin/sh
+
+die() {
+    echo "${@}"
+    exit 1
+}
+
+if [ -z "$ARCH" ]; then
+  ARCH="*"
+else
+    case ${ARCH} in
+    "x86_64")
+        ARCH="x86_64"
+        ;;
+    "aarch64"|"arm64")
+        ARCH="arm64"
+        ;;
+    *)
+        die "unsupported architecture: ${ARCH}"
+        ;;
+    esac
+fi
+
+if [ -z "$DISTRO" ]; then
+  DISTRO="*"
+fi
+
+if [ -z "$VERSION" ]; then
+  VERSION="*"
+fi
+
+BASE_DIR=$(dirname "$(realpath "$0")")
+ARCHIVE_DIR=$(realpath "$BASE_DIR/../archive")
+REPO_URL="https://github.com/aquasecurity/btfhub-archive.git"
+
+if [ ! -d "$ARCHIVE_DIR" ]; then
+    echo "Directory does not exist. Creating $ARCHIVE_DIR..."
+    mkdir -p "$ARCHIVE_DIR"
+fi
+
+# if the directory is already a git repository, skip cloning
+if [ -d "$ARCHIVE_DIR/.git" ]; then
+    echo "Directory is already a Git repository."
+else
+    # clone into the directory
+    git clone --sparse --filter=blob:none "$REPO_URL" "$ARCHIVE_DIR"
+fi
+
+# initialize sparse-checkout
+git -C "$ARCHIVE_DIR" sparse-checkout init --no-cone
+
+# write patterns for the files we want to pull
+echo "$DISTRO/$VERSION/$ARCH/*.btf.tar.xz" > "$ARCHIVE_DIR/.git/info/sparse-checkout"
+git -C "$ARCHIVE_DIR" sparse-checkout reapply || die "failed to reapply sparse-checkout"
+
+echo "Sparse checkout completed successfully in $ARCHIVE_DIR"