Only use substrate-wasm-builder when std feature is enabled. (#12790)

Co-authored-by: parity-processbot <>

substrate/bin/node/runtime/Cargo.toml

@@ -113,7 +113,7 @@ pallet-vesting = { version = "4.0.0-dev", default-features = false, path = "../.
 pallet-whitelist = { version = "4.0.0-dev", default-features = false, path = "../../../frame/whitelist" }
 
 [build-dependencies]
-substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder" }
+substrate-wasm-builder = { version = "5.0.0-dev", path = "../../../utils/wasm-builder", optional = true }
 
 [features]
 default = ["std"]
@@ -205,6 +205,7 @@ std = [
 	"sp-io/std",
 	"pallet-child-bounties/std",
 	"pallet-alliance/std",
+	"substrate-wasm-builder",
 ]
 runtime-benchmarks = [
 	"frame-benchmarking/runtime-benchmarks",

substrate/bin/node/runtime/build.rs

@@ -15,12 +15,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use substrate_wasm_builder::WasmBuilder;
-
 fn main() {
-	WasmBuilder::new()
-		.with_current_project()
-		.export_heap_base()
-		.import_memory()
-		.build()
+	#[cfg(feature = "std")]
+	{
+		substrate_wasm_builder::WasmBuilder::new()
+			.with_current_project()
+			.export_heap_base()
+			.import_memory()
+			.build();
+	}
 }