Buck: Fix lib/codemirror:jar rule by making it repeatable

Replace "mv" with "cp" in //lib/codemirror:jar target. Usage of "mv" is
wrong here, while it makes the rule not repeatable: when the rule is
changed and thus must be reevaluated, it cannot: css and js were moved
and cannot be accessed any more.

Note: That is expected that after applying this change the build of jar
is failing:

  $ buck build lib/codemirror:jar
  cp: cannot stat <path to /buck-out/gen/lib/codemirror/cm3.css>:
  No such file or directory

That's the bug this change is fixing.  To recover wipe out the Buck output
directory:

  rm -rf buck-out

Change-Id: I1bfc5bb10eaa52332043914641a72510c8e539c5
1 file changed