run.in: Detect binaries in builddir properly

run.in: Detect binaries in builddir properly

When attempting to run:

  libvirt.git/_build # ./run --selinux ./src/libvirtd

the following error is thrown:

  Refusing to change selinux context of file './src/libvirtd' outside build directory

which is obviously wrong. The problem is 'being inside of build
directory' is detected by simple progpath.startswith(builddir).
While builddir is an absolute path, progpath isn't necessarily.

And while looking into the code, I've noticed chcon() function
accessing variable outside its scope when printing out the path
it's working on.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>