os, runtime: remove unused implementations of os.sigpipe

Clean up instances that are unused since CL 6450058.

Change-Id: I0e9ae28cfa83fcc8abda8f5eca9c7dfc2c1c4ad1
Reviewed-on: https://go-review.googlesource.com/c/go/+/477396
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Bypass: Ian Lance Taylor <iant@golang.org>

src/os/file_posix.go

@@ -12,8 +12,6 @@ import (
 	"time"
 )
 
-func sigpipe() // implemented in package runtime
-
 // Close closes the File, rendering it unusable for I/O.
 // On files that support SetDeadline, any pending I/O operations will
 // be canceled and return immediately with an ErrClosed error.

src/os/file_unix.go

@@ -210,6 +210,8 @@ func newFile(fd uintptr, name string, kind newFileKind) *File {
 	return f
 }
 
+func sigpipe() // implemented in package runtime
+
 // epipecheck raises SIGPIPE if we get an EPIPE error on standard
 // output or standard error. See the SIGPIPE docs in os/signal, and
 // issue 11845.

src/runtime/os_plan9.go

@@ -69,11 +69,6 @@ func errstr() string
 
 type _Plink uintptr
 
-//go:linkname os_sigpipe os.sigpipe
-func os_sigpipe() {
-	throw("too many writes on closed pipe")
-}
-
 func sigpanic() {
 	gp := getg()
 	if !canpanic() {

src/runtime/os_windows.go

@@ -200,11 +200,6 @@ type mOS struct {
 	preemptExtLock uint32
 }
 
-//go:linkname os_sigpipe os.sigpipe
-func os_sigpipe() {
-	throw("too many writes on closed pipe")
-}
-
 // Stubs so tests can link correctly. These should never be called.
 func open(name *byte, mode, perm int32) int32 {
 	throw("unimplemented")