Prior to this commit, if the ssh-config command was invoked within
cygwin or msys2, it would show a regular windows style path for private
keys rather than a path that could be used within msys2 or cygwin. This
commit updates that behavior by converting all of the private key paths
to the proper msys2 or cygwin path if the platform is windows and the
command was invoked from one of those two shells.
Detecting cygwin via PATH contents can result in false positives
resulting in errors when using Vagrant on Windows outside of a
cygwin shell. Use environment based detection instead.
While VirtualBox has commented that they do not support UNC remote
paths (but do for long paths) it seems that remote paths can work.
If user provides UNC path, allow it to be used as-is.
Fixes#7011
This commit changes Vagrant::Util::Platform to cache the result of some
common operations. These values are highly unlikely to change over the
course of a single Vagrant run and they are only cached for that run.
