Pass keyfile via commandline arguments

src/main.rs

@@ -47,7 +47,7 @@ fn main() {
     } as *mut u8;
     assert_ne!(sync_memory, MAP_FAILED as *mut u8);
 
-    let private_file = File::open(env::var("KEY_FILE").expect("KEY_FILE environment variable missing")).expect("Cannot open KEY_FILE");
+    let private_file = File::open(&args[2]).expect("Cannot open KEY_FILE");
     let private_mem = unsafe {
         mmap(
             ptr::null_mut() as *mut c_void,