split proxmox-file-restore into its own crate

This also moves a couple of required utilities such as
logrotate and some file descriptor methods to pbs-tools.

Note that the logrotate usage and run-dir handling should be
improved to work as a regular user as this *should* (IMHO)
be a regular unprivileged command (including running
qemu given the kvm privileges...)

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

pbs-tools/src/fd.rs

@@ -0,0 +1,14 @@
+//! Raw file descriptor related utilities.
+
+use std::os::unix::io::RawFd;
+
+use anyhow::Error;
+use nix::fcntl::{fcntl, FdFlag, F_GETFD, F_SETFD};
+
+/// Change the `O_CLOEXEC` flag of an existing file descriptor.
+pub fn fd_change_cloexec(fd: RawFd, on: bool) -> Result<(), Error> {
+    let mut flags = unsafe { FdFlag::from_bits_unchecked(fcntl(fd, F_GETFD)?) };
+    flags.set(FdFlag::FD_CLOEXEC, on);
+    fcntl(fd, F_SETFD(flags))?;
+    Ok(())
+}