fix nasty edge case where we can't find guest additions on windows if they are on a different drive

common/config.go

@@ -74,12 +74,6 @@ func DownloadableURL(original string) (string, error) {
 				url.Path = url.Host
 				url.Host = ""
 			}
-
-			// For Windows absolute file paths, remove leading / prior to processing
-			// since net/url turns "C:/" into "/C:/"
-			if len(url.Path) > 0 && url.Path[0] == '/' {
-				url.Path = url.Path[1:len(url.Path)]
-			}
 		}
 
 		// Only do the filepath transformations if the file appears

common/download.go

@@ -15,6 +15,7 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"runtime"
 )
 
 // DownloadConfig is the configuration given to instantiate a new
@@ -129,6 +130,11 @@ func (d *DownloadClient) Get() (string, error) {
 		// locally and we don't make a copy. Normally we would copy or download.
 		log.Printf("[DEBUG] Using local file: %s", finalPath)
 
+		// Remove forward slash on absolute Windows file URLs before processing
+		if runtime.GOOS == "windows" && len(finalPath) > 0 && finalPath[0] == '/' {
+			finalPath = finalPath[1:]
+		}
+
 		// Keep track of the source so we can make sure not to delete this later
 		sourcePath = finalPath
 		if _, err = os.Stat(finalPath); err != nil {