Replace package _LIBRARIES by _LIBRARY and _INCLUDE_DIRS by
_INCLUDE_DIR. Move find_package_handle_standard_args for Oracle and DB2,
since this call should set _FOUND variable but not separate condition.
Fixes: QTBUG-89866
Change-Id: I54be2c2c4d7ba4b849a27139702861ecd937c444
Reviewed-by: Craig Scott <craig.scott@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>