all: add //go:build lines to assembly files

For golang/go#41184

Change-Id: Ica67fdbf2745ad2eef63dbb9ef70136e9e6fd348
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/319469
Trust: Tobias Klauser <[email protected]>
Run-TryBot: Tobias Klauser <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: tklauser

argon2/blamka_amd64.s

@@ -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 amd64 && gc && !purego
 // +build amd64,gc,!purego
 
 #include "textflag.h"

blake2b/blake2bAVX2_amd64.s

@@ -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 go1.7 && amd64 && gc && !purego
 // +build go1.7,amd64,gc,!purego
 
 #include "textflag.h"

blake2b/blake2b_amd64.s

@@ -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 amd64 && gc && !purego
 // +build amd64,gc,!purego
 
 #include "textflag.h"

blake2s/blake2s_386.s

@@ -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 386 && gc && !purego
 // +build 386,gc,!purego
 
 #include "textflag.h"

blake2s/blake2s_amd64.s

@@ -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 amd64 && gc && !purego
 // +build amd64,gc,!purego
 
 #include "textflag.h"

chacha20/chacha_arm64.s

@@ -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 go1.11 && gc && !purego
 // +build go1.11,gc,!purego
 
 #include "textflag.h"

chacha20/chacha_ppc64le.s

@@ -19,6 +19,7 @@
 // The differences in this and the original implementation are
 // due to the calling conventions and initialization of constants.
 
+//go:build gc && !purego
 // +build gc,!purego
 
 #include "textflag.h"

chacha20/chacha_s390x.s

@@ -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 gc && !purego
 // +build gc,!purego
 
 #include "go_asm.h"

chacha20poly1305/chacha20poly1305_amd64.s

@@ -4,6 +4,7 @@
 
 // This file was originally from https://golang.org/cl/24717 by Vlad Krasnov of CloudFlare.
 
+//go:build gc && !purego
 // +build gc,!purego
 
 #include "textflag.h"

curve25519/internal/field/_asm/fe_amd64_asm.go

@@ -17,6 +17,7 @@ import (
 
 func main() {
 	Package("golang.org/x/crypto/curve25519/internal/field")
+	Comment("//go:build amd64 && gc && !purego")
 	ConstraintExpr("amd64,gc,!purego")
 	feMul()
 	feSquare()