+ * `--[no-]preclean-build[=no|src|full]`: When doing an out-of-tree
+ build, controls whether the build directory is purged of leftover
+ contents *before* the build is run. The usual default is `no`.
+ For `cargo publish`, the default is `src`, which deletes
+ everything except the directory `target`. `full` means to clean
+ out that too.
+