os, internal/syscall/unix: consolidate Pipe implementations

All platforms with the pipe2 syscall now provide syscall.Pipe2.  Use it
to implement os.Pipe.

This also allows to drop the illumos-specific wrapper in
internal/sys/unix.

Change-Id: Ieb712a1498e86a389bad261e4e97c61c11d4bdd0
Reviewed-on: https://go-review.googlesource.com/c/go/+/390715
Trust: Tobias Klauser <[email protected]>
Run-TryBot: Tobias Klauser <[email protected]>
Trust: Matt Layher <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: tklauser

src/internal/syscall/unix/pipe2_illumos.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.
 
-//go:build dragonfly || freebsd || netbsd || openbsd
+//go:build dragonfly || freebsd || linux || netbsd || openbsd || solaris
 
 package os
 
@@ -15,7 +15,7 @@ func Pipe() (r *File, w *File, err error) {
 
 	e := syscall.Pipe2(p[0:], syscall.O_CLOEXEC)
 	if e != nil {
-		return nil, nil, NewSyscallError("pipe", e)
+		return nil, nil, NewSyscallError("pipe2", e)
 	}
 
 	return newFile(uintptr(p[0]), "|0", kindPipe), newFile(uintptr(p[1]), "|1", kindPipe), nil

src/os/pipe2_illumos.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.
 
-//go:build aix || darwin || (js && wasm) || (solaris && !illumos)
+//go:build aix || darwin || (js && wasm)
 
 package os