This change packages the api-ms-* DLLs and the VS 2015 CRT DLLs in all
of the VS package directories that we add to the path, so that they can
run without having the UCRT installed.

The Common7\IDE path was removed because it isn't actually packaged, in
VS 2013 or VS 2015, so adding it to the path is purely confusing.

In addition to changing the packaging script the installation script has
to change in order to continue if the UCRT cannot be installed. It
still makes sense to try to install it, and print a message saying where
the installer is, for the convenience of Google developers who may want
more flexibility in running VS 2015 binaries.

A 'calculating hash' message was added to make the mysterious hashing
hangs (which can be several minutes long) less mysterious.

BUG=440500

Review URL: https://codereview.chromium.org/1660723002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@298541 0039d316-1c4b-4281-b951-d872f2087c98