Remove/convert usages of msvs_cygwin_shell

(This was probably used to avoid problems on VS builds, but
we don't have that to worry about any more.)

R=joaodasilva@chromium.org
BUG=123026
TEST=remove app\policy\VERSION and policy_templates.zip and run ninja -C out\Debug pack_policy_templates

Review URL: https://codereview.chromium.org/142303002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245808 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245808