Avoid unnecessary build time dependency on fakeroot

It is possible to build ext4magic with no changes other than setting Rules-Requires-Root: no. The resulting deb is functionally the same as without, since debhelper and dpkg correctly normalizes ownership to root:root even when building as a normal user.

On avoiding fakeroot:

As useful as fakeroot has been, it is also quite fragile. As an example, a slightly out of date fakeroot can cause debs to be contaminated with non-root ownership #1024544. Additionally, fakeroot has one open unfixed RC bug filed against it that has made it unable to migrate to testing for a while.