Preserve checks/<pkg>/{new,old}/libraries.txt

[HenrikBengtsson]

Archive checks/<pkg>/{new,old}/libraries.txt so they survive revdep_reset(). These files contain:

$ cat checks/future.apply/new/libraries.txt 
Library: /c4/home/henrik/repositories/future/revdep/library/future/new
codetools    (0.2-18)
digest       (0.6.29)
environments (0.2.0-9000)
future       (1.25.0-9120)
globals      (0.15.0)
listenv      (0.8.0)
parallelly   (1.31.1)

Library: /c4/home/henrik/repositories/future/revdep/library/future.apply
codetools   (0.2-18)
digest      (0.6.29)
globals     (0.15.0)
listenv     (0.8.0)
markdown    (1.1)
mime        (0.12)
parallelly  (1.31.1)
R.cache     (0.15.0)
R.methodsS3 (1.8.1)
R.oo        (1.24.0)
R.rsp       (0.44.0)
R.utils     (2.11.0)
xfun        (0.31)

Archiving could be done by copying them to logs/<pkg>/{new,old}/libraries.txt.