all: add go:build lines (#23468)

Generated by go1.17 fmt ./...

crypto/secp256k1/dummy.go

@@ -1,3 +1,4 @@
+//go:build dummy
 // +build dummy
 
 // This file is part of a workaround for `go mod vendor` which won't vendor

crypto/secp256k1/panic_cb.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be found in
 // the LICENSE file.
 
-// +build !gofuzz
-// +build cgo
+//go:build !gofuzz && cgo
+// +build !gofuzz,cgo
 
 package secp256k1
 

crypto/secp256k1/scalar_mult_cgo.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be found in
 // the LICENSE file.
 
-// +build !gofuzz
-// +build cgo
+//go:build !gofuzz && cgo
+// +build !gofuzz,cgo
 
 package secp256k1
 

crypto/secp256k1/scalar_mult_nocgo.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be found in
 // the LICENSE file.
 
+//go:build gofuzz || !cgo
 // +build gofuzz !cgo
 
 package secp256k1

crypto/secp256k1/secp256.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be found in
 // the LICENSE file.
 
-// +build !gofuzz
-// +build cgo
+//go:build !gofuzz && cgo
+// +build !gofuzz,cgo
 
 // Package secp256k1 wraps the bitcoin secp256k1 C library.
 package secp256k1