pkg/system: update volumePath regex to allow returning earlier

The regex only matched volume paths without a trailing path-separator. In cases
where a path would be passed with a trailing path-separator, it would depend on
further code in mkdirall to strip the trailing slash, then to perform the regex
again in the next iteration.

While regexes aren't ideal, we're already executing this one, so we may as well
use it to match those situations as well (instead of executing it twice), to
allow us to return early.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

pkg/system/filesys_windows.go

@@ -13,8 +13,9 @@ import (
 const SddlAdministratorsLocalSystem = "D:P(A;OICI;GA;;;BA)(A;OICI;GA;;;SY)"
 
 // volumePath is a regular expression to check if a path is a Windows
-// volume path (e.g., "\\?\Volume{4c1b02c1-d990-11dc-99ae-806e6f6e6963}".
-var volumePath = regexp.MustCompile(`^\\\\\?\\Volume{[a-z0-9-]+}$`)
+// volume path (e.g., "\\?\Volume{4c1b02c1-d990-11dc-99ae-806e6f6e6963}"
+// or "\\?\Volume{4c1b02c1-d990-11dc-99ae-806e6f6e6963}\").
+var volumePath = regexp.MustCompile(`^\\\\\?\\Volume{[a-z0-9-]+}\\?$`)
 
 // MkdirAllWithACL is a custom version of os.MkdirAll modified for use on Windows
 // so that it is both volume path aware, and can create a directory with