POSIX: unlink() returns EPERM (-1) on failure.

[iMoD1998]

*Describe the bug
Similar to #1442, unlink returns EPERM on failure resulting in some implementations of tar (specifically in busybox) to fail extracting. This likely due to tar trying to remove old files before extracting and if this fails it assumes directory isn't writable due to EPERM.

Expected behavior
Unlink should return proper error code such as ENOENT when a directory doesnt exist etc.