Function write_platform_sibling 

pub(crate) fn write_platform_sibling(
    base: &OsStr,
    output: &Path,
    meta: &PlatformMeta,
    ext: &str,
    bytes: &[u8],
) -> Result<()>

Write a per-platform sibling file (a JSON identity document, an SNP ID block signing payload, or a CoRIM launch endorsement) next to output, named <base>-<isolation><ext>. ext must include the leading dot.