fix last-line \n bug.

in your test file, it has a `\n` line in end, so in test.c `alpha` should be fixed like this PR, that updated related lines in fs.c to fix the bug.

Plus, this bug is the culprit of https://github.com/clibs/clib/issues/25, because when package.json like:
```json
{
  "dependencies": {}
}
```
Then the result of `fs_read` is:
```json
{
  "dependencies":{}
```