Revert "[!!!][TASK] Merge typo3/sysext/core/Build/ to Build/ directory"

The change does not play well with a symlinked core and
is reverted for now.

This reverts commit e6474fe5.

Change-Id: I74ddc970a20d34a4d105a91cbdd5f12486c9568b
Releases: master
Reverts: #67076
Reviewed-on: http://review.typo3.org/39649


Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>