sbuild-tmp-cache-xxx files/dirs lack complete cleanup

[dtrudg]

Version of Singularity

main / 4.3

Describe the bug

When explicit or implicit builds are run with the cache disabled, an sbuild-tmp-cache-xxx file or dir may be left in TMPDIR.

For example, after running the e2e test suit, in TMPDIR a number of these can be seen:

-rw-------.  1 root     root     3.2M Jan  8 10:42 sbuild-tmp-cache-1031581445
-rw-------.  1 root     root        0 Jan  8 10:42 sbuild-tmp-cache-1107935441
-rw-------.  1 root     root        0 Jan  8 10:42 sbuild-tmp-cache-1147031060
-rw-------.  1 ec2-user ec2-user    0 Jan  8 10:42 sbuild-tmp-cache-1147580832
...

The cache disabled flow needs to clean these up properly.