hello world example working

src/os.cpp

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2015 Andrew Kelley
+ *
+ * This file is part of zig, which is MIT licensed.
+ * See http://opensource.org/licenses/MIT
+ */
+
+#include "os.hpp"
+#include "util.hpp"
+
+#include <unistd.h>
+#include <errno.h>
+
+void os_spawn_process(const char *exe, ZigList<const char *> &args, bool detached) {
+    pid_t pid = fork();
+    if (pid == -1)
+        zig_panic("fork failed");
+    if (pid != 0)
+        return;
+    if (detached) {
+        if (setsid() == -1)
+            zig_panic("process detach failed");
+    }
+
+    const char **argv = allocate<const char *>(args.length + 2);
+    argv[0] = exe;
+    argv[args.length + 1] = nullptr;
+    for (int i = 0; i < args.length; i += 1) {
+        argv[i + 1] = args.at(i);
+    }
+    execvp(exe, const_cast<char * const *>(argv));
+    zig_panic("execvp failed: %s", strerror(errno));
+}