[MacPorts] #54773: port:libgcc/port:gcc7: proposed modifications, efficiency + libc++ support

[MacPorts]

#54773: port:libgcc/port:gcc7: proposed modifications, efficiency + libc++ support
--------------------------+----------------------
  Reporter:  RJVB         |      Owner:
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:  haspatch
      Port:  gcc7 libgcc  |
--------------------------+----------------------

Comment (by RJVB):

 I would hope that gccX+with_libgcc and gccY+with_libgcc don't conflict
 (except currently for gcc7 and gcc8) because only one of them installs
 things into lib/libgcc . I admit I haven't yet given thought to this
 except in the back of my mind because at the moment conflicts are handled
 at the level of port:libgcc . You still need to install that port, I'll
 have another look if `port:libgcc+stub` really needs to depend on its
 corresponding `port:gcc` or if I can restore the opposite dependency.

 I noticed another thing: back in 2013 you re-enabled the no-bootstrap
 build for libgcc, which was undone in 2015 when Ryan committed a new
 version. Was that a casualty or was there a solid reason for this? I'm
 currently trying a "full" libgcc build with `--disable-bootstrap`, from
 what I understand this should work on at least 10.8 and up.

--
Ticket URL: <https://trac.macports.org/ticket/54773#comment:22>
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