internal/syscall/unix: don't define libc_getentropy_trampoline on ios

It is only used on Darwin. This fixes "go vet" on ios.

Fixes #61667

Change-Id: Iaf00fcee5d89eb8e454f75bb1c0ea62c3950b684
Reviewed-on: https://go-review.googlesource.com/c/go/+/514495
Reviewed-by: Bryan Mills <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>

Author: ianlancetaylor

src/internal/syscall/unix/asm_darwin.s

@@ -4,7 +4,6 @@
 
 #include "textflag.h"
 
-TEXT ·libc_getentropy_trampoline(SB),NOSPLIT,$0-0; JMP libc_getentropy(SB)
 TEXT ·libc_getaddrinfo_trampoline(SB),NOSPLIT,$0-0; JMP libc_getaddrinfo(SB)
 TEXT ·libc_freeaddrinfo_trampoline(SB),NOSPLIT,$0-0; JMP libc_freeaddrinfo(SB)
 TEXT ·libc_getnameinfo_trampoline(SB),NOSPLIT,$0-0; JMP libc_getnameinfo(SB)

src/internal/syscall/unix/getentropy_darwin.s

@@ -0,0 +1,9 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build darwin && !ios
+
+#include "textflag.h"
+
+TEXT ·libc_getentropy_trampoline(SB),NOSPLIT,$0-0; JMP libc_getentropy(SB)