tests/fuzzers/bls12381: deactivate BLS fuzzer when CGO_ENABLED=0 (#28653)

tests/fuzzers/bls12381: deactivate fuzzer when CGO_ENABLED=0

tests/fuzzers/bls12381/bls12381_fuzz.go

@@ -14,6 +14,9 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
+//go:build cgo
+// +build cgo
+
 package bls
 
 import (

tests/fuzzers/bls12381/bls12381_test.go

@@ -14,6 +14,9 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
+//go:build cgo
+// +build cgo
+
 package bls
 
 import "testing"