Make nulldrv a small C++ program

src/drivers/nulldrv/main.cpp

@@ -1 +1,22 @@
-int main(int argc, const char **argv) { return 0; }
+#include <stdint.h>
+#include <stdlib.h>
+
+extern "C" {
+	int32_t getpid();
+	void sleep(uint64_t til);
+	void debug();
+
+	int main(int, const char **);
+}
+
+
+int
+main(int argc, const char **argv)
+{
+	int32_t pid = getpid();
+	debug();
+	for (int i = 1; i < 5; ++i)
+		sleep(i*10);
+	debug();
+	return 0;
+}