Clarify how to install Qt on 10.9
passenger 4.0.25

Closes #24505.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
leiningen 2.3.4

Closes #24506.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
gabedit: disable openmp when using clang

Fixes #24467.