ceylon: correctly install manpages.

Closes #24178.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
Extract archflags
Extract optflags
Remove outdated comment
Add ENV.O0 to stdenv
Simplify ENV.0x methods in stdenv
Allow changing the optimization level under superenv
clisp: enable superenv
pdnsrec: enable superenv