This script installs libiodbc from brew and adds it to
CPLUS_INCLUDE_PATH and LIBRARY_PATH thus enabling configure to
find it and thus enabling odbc support for qt build on macOS.
Task-number: QTBUG-58956
Change-Id: I7f865800b580a87afcc480534da57ee546c74406
Reviewed-by: Antti Kokko <antti.kokko@qt.io>