docs: Document 'make EXTRAVERSION=xyz' and scripts/tarball.sh

Document the existence of the EXTRAVERSION field and the information
expected to be present in it.  Document the use of tarball.sh in build
environments that lack git.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
1 file changed
tree: 74d1445fc2892aa043c857c00b5b53ac79204cef
  1. .gitignore
  2. COPYING
  3. COPYING.LESSER
  4. Makefile
  5. README
  6. docs/
  7. scripts/
  8. src/
  9. vgasrc/