As discussed in #30556, if openssl is enabled using --enable-openssl and neither openssl nor python3 are available as system packages, this makes sure that openssl is built before python3.

If system openssl is found via #30557, then --enable-openssl does NOT trigger building openssl. Use --enable-openssl --without-system-openssl if this is desired.

Part of #21700 Meta-ticket: Declare "optional" dependencies of packages (a package manager's suggested/recommended packages)

CC: @mwageringel @slel @dimpase @orlitzky @jhpalmieri

Component: build

Author: Matthias Koeppe

Branch/Commit: 0c394ca

Reviewer: John Palmieri

Issue created by migration from https://trac.sagemath.org/ticket/30560