Do not create a BSD local hierarchy under ${STAGEDIR}${LINUXBASE} when
USE_LINUX=yes and PREFIX!=LINUXBASE.
This is not needed and creates a bunch of stage orphaned directories.

PR: ports/184477
Approved by: portmgr (bapt)
Tested by: poudriere bulk -t games/dsnake emulators/rtc www/linux-f10-flashplugin11 (no error, no orphans)