Fix linux build.

src/App_unix.cpp

@@ -0,0 +1,66 @@
+/* XMRig
+ * Copyright 2010      Jeff Garzik <jgarzik@pobox.com>
+ * Copyright 2012-2014 pooler      <pooler@litecoinpool.org>
+ * Copyright 2014      Lucas Jones <https://github.com/lucasjones>
+ * Copyright 2014-2016 Wolf9466    <https://github.com/OhGodAPet>
+ * Copyright 2016      Jay D Dee   <jayddee246@gmail.com>
+ * Copyright 2016-2017 XMRig       <support@xmrig.com>
+ *
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#include <stdlib.h>
+#include <signal.h>
+#include <errno.h>
+#include <unistd.h>
+
+
+#include "App.h"
+#include "Console.h"
+#include "Cpu.h"
+#include "Options.h"
+
+
+void App::background()
+{
+    if (m_options->affinity() != -1L) {
+        Cpu::setAffinity(-1, m_options->affinity());
+    }
+
+    if (!m_options->background()) {
+        return;
+    }
+
+    int i = fork();
+    if (i < 0) {
+        exit(1);
+    }
+
+    if (i > 0) {
+        exit(0);
+    }
+
+    i = setsid();
+
+    if (i < 0) {
+        LOG_ERR("setsid() failed (errno = %d)", errno);
+    }
+
+    i = chdir("/");
+    if (i < 0) {
+        LOG_ERR("chdir() failed (errno = %d)", errno);
+    }
+}