arm/armspec, vendor/rsc.io/pdf: don't build on 386 until Go 1.8

This won't be fixed until the SSA backend in Go 1.8, so don't even try
to build. It just clutters the dashboard with red.

Updates golang/go#12840 (out of fixed registers)
Updates golang/go#11811 (subrepos need to be green)

Change-Id: I25b3db4d3bd47d16e7e42a55429b343dc27f9f43
Reviewed-on: https://go-review.googlesource.com/24942
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/arm/armspec/spec.go b/arm/armspec/spec.go
index f76fab0..e02d092 100644
--- a/arm/armspec/spec.go
+++ b/arm/armspec/spec.go
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !386 go1.8
+// ... see golang.org/issue/12840
+
 // Armspec reads the ``ARM Architecture Reference Manual''
 // to collect instruction encoding details and writes those details to standard output
 // in JSON format.
diff --git a/vendor/rsc.io/pdf/lex.go b/vendor/rsc.io/pdf/lex.go
index ee73fd9..85bfdcc 100644
--- a/vendor/rsc.io/pdf/lex.go
+++ b/vendor/rsc.io/pdf/lex.go
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !386 go1.8
+// ... see golang.org/issue/12840
+
 // Reading of PDF tokens and objects from a raw byte stream.
 
 package pdf
diff --git a/vendor/rsc.io/pdf/page.go b/vendor/rsc.io/pdf/page.go
index 9c7d688..6669907 100644
--- a/vendor/rsc.io/pdf/page.go
+++ b/vendor/rsc.io/pdf/page.go
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !386 go1.8
+// ... see golang.org/issue/12840
+
 package pdf
 
 import (
diff --git a/vendor/rsc.io/pdf/ps.go b/vendor/rsc.io/pdf/ps.go
index 90c551e..69292aa 100644
--- a/vendor/rsc.io/pdf/ps.go
+++ b/vendor/rsc.io/pdf/ps.go
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !386 go1.8
+// ... see golang.org/issue/12840
+
 package pdf
 
 import (
diff --git a/vendor/rsc.io/pdf/read.go b/vendor/rsc.io/pdf/read.go
index da6c2c6..84cb17a 100644
--- a/vendor/rsc.io/pdf/read.go
+++ b/vendor/rsc.io/pdf/read.go
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !386 go1.8
+// ... see golang.org/issue/12840
+
 // Package pdf implements reading of PDF files.
 //
 // Overview