getcwd_syscall() updates

[ve1nard]

Description

Fixes # (issue)

The following changes include a small fix for checking null pointers, more elaborate comments, and new unit tests for getcwd_syscall().

Type of change

• More detailed comments for getcwd_syscall()
• Added a condition to error-out null pointers passed as buf argument
• New unit tests for getcwd_syscall()

How Has This Been Tested?

To run the tests, we need to run cargo test --lib command inside the safeposix-rust directory.

All the tests are present under this directory: lind_project/src/safeposix-rust/src/tests/fs_tests.rs

• Test A - lut_lind_fs_getcwd_valid_args()
• Test B - ut_lind_fs_getcwd_invalid_args()

Checklist:

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been added to a pull request and/or merged in other modules (native-client, lind-glibc, lind-project)

[rennergade]

@Anway-Agte can you review this before Rupesh does?

[rupeshkoushik07]

looks good to me!

[rennergade]

Minor comment about the EFAULT check. I also don't really know why there are so many extra files in this PR.

Otherwise really great job on this one, incredibly thorough.

[rennergade]

Awesome. Great job!