fix: test case ut_lind_fs_mmap_zerolen

[ChinmayShringi]

Description

Fixes # (issue)

This PR updates the ut_lind_fs_mmap_zerolen test to correctly handle the case where mmap_syscall is passed a length of 0. Passing 0 as the length to mmap should result in an invalid argument error (EINVAL). Previously, the test directly compared the result of mmap_syscall with -(Errno::EINVAL as i32), which was incorrect. Now, the test checks for mmap_syscall returning -1 and verifies that errno is set to EINVAL.

Changes:

• Modified the test to assert that mmap_syscall returns -1 upon failure due to the zero-length argument.
• Added checks to verify that errno is set to EINVAL, which indicates the invalid argument error for passing a zero-length value to mmap.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• cargo test ut_lind_fs_mmap_zerolen

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)