os: skip TestFifoEOF on android

TestFifoEOF fails on android because the mkfifo syscall is not allowed:

--- FAIL: TestFifoEOF (0.00s)
    fifo_test.go:39: permission denied

Change-Id: I007ff359831525add39cec34de4b3d3cd3adb047
Reviewed-on: https://go-review.googlesource.com/118815
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/os/fifo_test.go

@@ -23,7 +23,10 @@ import (
 
 // Issue 24164.
 func TestFifoEOF(t *testing.T) {
-	if runtime.GOOS == "openbsd" {
+	switch runtime.GOOS {
+	case "android":
+		t.Skip("skipping on Android; mkfifo syscall not available")
+	case "openbsd":
 		// On OpenBSD 6.2 this test just hangs for some reason.
 		t.Skip("skipping on OpenBSD; issue 25877")
 	}