Added execv() and system().

src/include/unistd.h

@@ -0,0 +1,24 @@
+#ifndef _UNISTD_H
+#define _UNISTD_H
+
+#include <stddef.h>
+#include <stdarg.h>
+
+extern int execv ( const char *command, char * const argv[] );
+
+/**
+ * Execute command
+ *
+ * @v command		Command name
+ * @v arg ...		Argument list (starting with argv[0])
+ * @ret rc		Command exit status
+ *
+ * This is a front end to execv().
+ */
+#define execl( command, arg, ... ) ( {					\
+		char * const argv[] = { (arg), ## __VA_ARGS__, NULL };	\
+		int rc = execv ( (command), argv );			\
+		rc;							\
+	} )
+
+#endif /* _UNISTD_H */