doc: minor updates to build script, again
doc: minor updates to build script, again

  - Mention why configure script is missing from GIT
  - Adjust command line for enabling Finit debug
  - Plus some minor formatting issues

Signed-off-by: Joachim Wiberg <583c295fd7602c168ad814279bbc3894ba65f5d6@gmail.com>

troglobit/finit,troglobit/finit