conserver 8.1.19
Implement MacOS.dev_tools_prefix a different way

Avoid producing a dev_tools_path of "//usr/bin".

Fixes #24751.
Closes #24754.
Add conflicts_with annotations for mysql-connector-c

Fixes #24756.
ical-buddy: respect compiler selection

Fixes mistydemeo/tigerbrew#144.
midnight-commander: requires openssl on Leopard

Fixes mistydemeo/tigerbrew#141.
transmission: requires curl on Leopard

Fixes mistydemeo/tigerbrew#143.