[MacPorts] #54216: zlib +ng (and +cloudflare) accelerated variants

[MacPorts]

#54216: zlib +ng (and +cloudflare) accelerated variants
--------------------------+------------------------
  Reporter:  RJVB         |      Owner:  ryandesign
      Type:  enhancement  |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:  haspatch
      Port:  zlib         |
--------------------------+------------------------

Comment (by RJVB):

 An alternative that might be easier to deploy than `provides` or
 `alternative_for` syntax would be to add a lookup (or depspec rewriter)
 step.

 {{{
 port:foo -> "foo"

 if look up "foo" in a table (dict?) (or us the entire port:foo depspec as
 key)
     use the returned expression (say path:libz.dylib) to determine if foo
 is available or not
 else
     just use the port:foo depspec
 }}}

 The table or dict would be populated with the (probably few) ports for
 which their are known/official alternatives that aren't already handled
 through dedicated portgroups.

 Would such an extra step incur a large performance hit?

--
Ticket URL: <https://trac.macports.org/ticket/54216#comment:9>
MacPorts <https://www.macports.org/>
Ports system for macOS