Revert 231164 "Move git cache_dir into gclient spec string."
Revert 231164 "Move git cache_dir into gclient spec string."

This caused win bots to do full syncs, which overwhelmed chrome's svn servers.

Example failure: http://build.chromium.org/p/chromium/builders/Win/builds/17578

> Move git cache_dir into gclient spec string.
>
> This will let us actually start using the git cache_dir. Previously, when it was
> simply appended to the command as --cache_dir=, it would get ignored or
> overridden since the command also contained --spec=.
>
> R=iannucci@chromium.org, maruel@chromium.org
> BUG=295119
>
> Review URL: https://codereview.chromium.org/44763002

R=cmp@chromium.org

Review URL: https://codereview.chromium.org/46693002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@231186 0039d316-1c4b-4281-b951-d872f2087c98

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