unix: use pselect on amd64 to satisfy Android

This is yet another syscall that needs to be changed around for
Android's seccomp. We already do this in MIPS64 and ARM64, but
apparently forgot about AMD64.

Change-Id: I42c8a4653a55d4714dacfaf7add14012f428c992
Reviewed-on: https://go-review.googlesource.com/109835Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

unix/syscall_linux_amd64.go

@@ -29,7 +29,15 @@ package unix
 //sys	Pread(fd int, p []byte, offset int64) (n int, err error) = SYS_PREAD64
 //sys	Pwrite(fd int, p []byte, offset int64) (n int, err error) = SYS_PWRITE64
 //sys	Seek(fd int, offset int64, whence int) (off int64, err error) = SYS_LSEEK
-//sys	Select(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timeval) (n int, err error)
+
+func Select(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timeval) (n int, err error) {
+	var ts *Timespec
+	if timeout != nil {
+		ts = &Timespec{Sec: timeout.Sec, Nsec: timeout.Usec * 1000}
+	}
+	return Pselect(nfd, r, w, e, ts, nil)
+}
+
 //sys	sendfile(outfd int, infd int, offset *int64, count int) (written int, err error)
 //sys	Setfsgid(gid int) (err error)
 //sys	Setfsuid(uid int) (err error)

unix/zsyscall_linux_amd64.go

@@ -1795,17 +1795,6 @@ func Seek(fd int, offset int64, whence int) (off int64, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func Select(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timeval) (n int, err error) {
-	r0, _, e1 := Syscall6(SYS_SELECT, uintptr(nfd), uintptr(unsafe.Pointer(r)), uintptr(unsafe.Pointer(w)), uintptr(unsafe.Pointer(e)), uintptr(unsafe.Pointer(timeout)), 0)
-	n = int(r0)
-	if e1 != 0 {
-		err = errnoErr(e1)
-	}
-	return
-}
-
-// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
-
 func sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
 	r0, _, e1 := Syscall6(SYS_SENDFILE, uintptr(outfd), uintptr(infd), uintptr(unsafe.Pointer(offset)), uintptr(count), 0, 0)
 	written = int(r0)