commit the current generated proxmox-backup-qemu.h as
'current-api.h' and run `diff -up` between the two in build
steps, so any changes to the C api are caught at build time.
cbindgen seems to be using a BTreeMap for the data, so it
should always come out sorted, so this should be a
stable-enough check.
Link: https://github.com/eqrion/cbindgen/issues/12
Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
