Tools usually expect the index files to be in the source tree, eg. emacs.
This is already the case when doing out-of-tree builds, but with in-tree
builds they end up in the build directory.

Force cscope, ctags and etags to put them in the source tree.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <160277334665.1754102.10921580280105870386.stgit@bahia.lan>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>