[MacPorts] #55471: Use separate portindexes for libc++ on older systems

[MacPorts]

#55471: Use separate portindexes for libc++ on older systems
--------------------------+----------------------------
  Reporter:  ryandesign   |      Owner:  neverpanic
      Type:  enhancement  |     Status:  assigned
  Priority:  Normal       |  Milestone:  MacPorts 2.5.0
 Component:  base         |    Version:
Resolution:               |   Keywords:
      Port:               |
--------------------------+----------------------------
Changes (by neverpanic):

 * status:  new => assigned
 * owner:   => neverpanic


--
Ticket URL: <https://trac.macports.org/ticket/55471#comment:8>
MacPorts <https://www.macports.org/>
Ports system for macOS