unix: add Pipe2 for solaris

We already implement Pipe2 for illumos and it seems solaris provides the
pipe2 syscall as well, see
https://docs.oracle.com/cd/E88353_01/html/E37841/pipe2-2.html.

Fixes golang/go#40613

Change-Id: I135cb1e78e6c67567d30d7eed266d00ef8fd6c3a
Reviewed-on: https://go-review.googlesource.com/c/sys/+/283032
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matt Layher <mdlayher@gmail.com>

unix/zsyscall_illumos_amd64.go

@@ -14,22 +14,19 @@ import (
 //go:cgo_import_dynamic libc_writev writev "libc.so"
 //go:cgo_import_dynamic libc_pwritev pwritev "libc.so"
 //go:cgo_import_dynamic libc_accept4 accept4 "libsocket.so"
-//go:cgo_import_dynamic libc_pipe2 pipe2 "libc.so"
 
 //go:linkname procreadv libc_readv
 //go:linkname procpreadv libc_preadv
 //go:linkname procwritev libc_writev
 //go:linkname procpwritev libc_pwritev
 //go:linkname procaccept4 libc_accept4
-//go:linkname procpipe2 libc_pipe2
 
 var (
 	procreadv,
 	procpreadv,
 	procwritev,
 	procpwritev,
-	procaccept4,
-	procpipe2 syscallFunc
+	procaccept4 syscallFunc
 )
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
@@ -102,13 +99,3 @@ func accept4(s int, rsa *RawSockaddrAny, addrlen *_Socklen, flags int) (fd int,
 	}
 	return
 }
-
-// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
-
-func pipe2(p *[2]_C_int, flags int) (err error) {
-	_, _, e1 := rawSysvicall6(uintptr(unsafe.Pointer(&procpipe2)), 2, uintptr(unsafe.Pointer(p)), uintptr(flags), 0, 0, 0, 0)
-	if e1 != 0 {
-		err = e1
-	}
-	return
-}