Add BPF Rust noop example (#316)

web3.js/examples/bpf-rust-noop/build.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+
+cd "$(dirname "$0")"
+
+cargo install xargo
+
+set -ex
+
+# Ensure the sdk is installed
+../../bpf-sdk/scripts/install.sh
+rustup override set bpf
+
+export RUSTFLAGS="$RUSTFLAGS \
+    -C lto=no \
+    -C opt-level=2 \
+    -C link-arg=-Tbpf.ld \
+    -C link-arg=-z -C link-arg=notext \
+    -C link-arg=--Bdynamic \
+    -C link-arg=-shared \
+    -C link-arg=--entry=entrypoint \
+    -C linker=../../bpf-sdk/llvm-native/bin/ld.lld"
+export XARGO_HOME="$PWD/target/xargo"
+export XARGO_RUST_SRC="../../bpf-sdk/rust-bpf-sysroot/src"
+# export XARGO_RUST_SRC="../../../../../rust-bpf-sysroot/src"
+xargo build --target bpfel-unknown-unknown --release -v
+
+{ { set +x; } 2>/dev/null; echo Success; }