Add debian_wheezy_i386-sysroot to .gitignore.

TBR=derat@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/117323009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242961 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242961