`platform_volumes` has been gated to Linux since it was written, but the
eight items it is built from were not, so every Android build compiled a
`/proc/mounts` parser it could never call and then printed eight dead-code
warnings about it. Real warnings hide in that kind of noise.
Gated per item rather than moved into a module, because the file already
draws the line that way one function above and two patterns for one idea
is worse than a repeated attribute.
The tests go with them. They parse a mount table and assert on names like
`mmcblk0p1`, so they are as Linux-bound as the code they exercise, and
`Path` turns out to be too -- only the reader borrows one, where `Volume`
owns its own.
Android now builds dr-plat with no warnings at all.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>