Ignore all the versioned git directories.

R=maruel@chromium.org

Review URL: https://codereview.chromium.org/172003003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@252297 0039d316-1c4b-4281-b951-d872f2087c98

.gitignore

@@ -22,7 +22,7 @@
 # Ignore locations where third-party tools are placed during bootstrapping.
 /python*_bin
 /git_bin
-/git-1.8.0_bin
+/git-*_bin
 /svn_bin
 /win_toolchain/vs2013_files
 /win_toolchain/.timestamps