stripExts: don't use a cutset when removing extension

I misread what strings.Trim does, the 2nd param is a _cut set_, so this
was removing any occurance any characters in the 2nd param. Since the
file extension is always a suffix, this uses TrimSuffix.

Fixes a bug where 'virtio_blk.ko' was being trimmed to 'virtio_bl'

main.go

@@ -614,7 +614,7 @@ func stripExts(file string) string {
 		if filepath.Ext(file) == "" {
 			break
 		}
-		file = strings.Trim(file, filepath.Ext(file))
+		file = strings.TrimSuffix(file, filepath.Ext(file))
 	}
 	return file
 }