Do not add additional newline if the .ninja_log ends with newline.
Do not add additional newline if the .ninja_log ends with newline.

In https://codereview.chromium.org/1011343002, newline is added
before adding additional text regardless of what it is.
It caused parse error on chromium_build_stats.

BUG=470599

Review URL: https://codereview.chromium.org/1041543002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@294621 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build