install: remove a to_string_lossy

[oech3]

lossy conversion is overkill just for checking last byte.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.
Note: The gnu test tests/env/env-signal-handler was skipped on 'main' but is now failing.

[xtqqczze]

As per #12306 (comment), this change might not be sound for Windows.

[oech3]

This just checks last byte. Not unsound.

[xtqqczze]

On further investigation, I think this change is sound as long as MAIN_SEPARATOR is guaranteed to be an ASCII character. In that case, its byte value is necessarily a non-continuation byte in the WTF-8 encoding used by Windows. It may be worth documenting this assumption in a comment to make it clear why this is sound.

cc: @ChrisDenton

[oech3]

I think comment is not needed since

MAIN_SEPARATOR is guaranteed to be an ASCII character.

is trivial.

[ChrisDenton]

On further investigation, I think this change is sound as long as MAIN_SEPARATOR is guaranteed to be an ASCII character

Yes, ASCII is perfectly fine in all cases.