deps: do not add extra newline in log file

The commit in v0.10 (431eb172) that
backported the original change
(https://codereview.chromium.org/806143002) did add an extra newline
because the logging facilities in v0.10's V8 do not add one.

When merging this commit in v0.12, V8's logging facilities now
automatically add the newline character, and the debug builds assert if
one is already present.