- reduce log noise by showing 'Uninstalling' message only if the file
exists. (and a different message otherwise)
- replace cmake `rm` command with `file(REMOVE)`. For efficiency.
Show manual message if the file could not be deleted.
Ref: https://cmake.org/cmake/help/v3.18/command/file.html#remove
Follow-up to 6d008352c6#22193
- reduce log noise by showing 'Uninstalled' only if the deletion was
successful. (and a different message otherwise)
- display `DESTDIR` env value if set.
- drop checking, setting and showing `CMAKE_INSTALL_PREFIX`.
The value was never predefined, also not used, besides showing it,
and showing it is misleading because `--prefix` may override the
configure-time value, and also superfluous because the filenames
are showing the actual prefix anyway.
Follow-up to 27e2a4733cCloses#22201
88d85916f2