[dev.boringcrypto] crypto/internal/boring: fall back to standard crypto when using -msan

The syso is not compiled with -fsanitize=memory, so don't try to use it.
Otherwise the first time it calls out to memcmp, memcmp complains
that it is being asked to compare uninitialized memory.

Change-Id: I85ab707cfbe64eded8e110d4d6b40d1b75f50541
Reviewed-on: https://go-review.googlesource.com/63916
Reviewed-by: Adam Langley <agl@golang.org>

src/crypto/internal/boring/aes.go

@@ -5,6 +5,7 @@
 // +build linux,amd64
 // +build !android
 // +build !cmd_go_bootstrap
+// +build !msan
 
 package boring
 

src/crypto/internal/boring/boring.go

@@ -5,6 +5,7 @@
 // +build linux,amd64
 // +build !android
 // +build !cmd_go_bootstrap
+// +build !msan
 
 package boring
 

src/crypto/internal/boring/ecdsa.go

@@ -5,6 +5,7 @@
 // +build linux,amd64
 // +build !android
 // +build !cmd_go_bootstrap
+// +build !msan
 
 package boring
 

src/crypto/internal/boring/hmac.go

@@ -5,6 +5,7 @@
 // +build linux,amd64
 // +build !android
 // +build !cmd_go_bootstrap
+// +build !msan
 
 package boring
 

src/crypto/internal/boring/notboring.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !linux !amd64 cmd_go_bootstrap android !cgo
+// +build !linux !amd64 !cgo android cmd_go_bootstrap msan
 
 package boring
 

src/crypto/internal/boring/rand.go

@@ -5,6 +5,7 @@
 // +build linux,amd64
 // +build !android
 // +build !cmd_go_bootstrap
+// +build !msan
 
 package boring
 

src/crypto/internal/boring/rsa.go

@@ -5,6 +5,7 @@
 // +build linux,amd64
 // +build !android
 // +build !cmd_go_bootstrap
+// +build !msan
 
 package boring
 

src/crypto/internal/boring/sha.go

@@ -5,6 +5,7 @@
 // +build linux,amd64
 // +build !android
 // +build !cmd_go_bootstrap
+// +build !msan
 
 package boring