net/http: Don't try to trace sendfile64 on alpha.

From Uros Bizjak.

From-SVN: r201206

libgo/go/net/http/fs_test.go

@@ -696,8 +696,13 @@ func TestLinuxSendfile(t *testing.T) {
 	}
 	defer ln.Close()
 
+	trace := "trace=sendfile"
+	if runtime.GOARCH != "alpha" {
+		trace = trace + ",sendfile64"
+	}
+
 	var buf bytes.Buffer
-	child := exec.Command("strace", "-f", "-q", "-e", "trace=sendfile,sendfile64", os.Args[0], "-test.run=TestLinuxSendfileChild")
+	child := exec.Command("strace", "-f", "-q", "-e", trace, os.Args[0], "-test.run=TestLinuxSendfileChild")
 	child.ExtraFiles = append(child.ExtraFiles, lnf)
 	child.Env = append([]string{"GO_WANT_HELPER_PROCESS=1"}, os.Environ()...)
 	child.Stdout = &buf