Ignore rustflags set by the build system when compiling wasm payload (#617)

diff --git a/examples/python/wasm_rust_psi_payload/Makefile b/examples/python/wasm_rust_psi_payload/Makefile
index 865f23c..34844d1 100755
--- a/examples/python/wasm_rust_psi_payload/Makefile
+++ b/examples/python/wasm_rust_psi_payload/Makefile
@@ -16,7 +16,7 @@
 # under the License.
 
 all:
-	@cargo build --target wasm32-unknown-unknown --release
+	@RUSTFLAGS='' cargo build --target wasm32-unknown-unknown --release
 	@wasm-gc target/wasm32-unknown-unknown/release/wasm_rust_psi_payload.wasm
 
 clean: