[MacPorts] #58442: gcc9 (and other gccN) fails to install on Mojave, Xcode-10.2.1

[MacPorts]

#58442: gcc9 (and other gccN) fails to install on Mojave, Xcode-10.2.1
-------------------------+--------------------
  Reporter:  mouse07410  |      Owner:  (none)
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:
Resolution:              |   Keywords:
      Port:  gcc9        |
-------------------------+--------------------

Comment (by kencu):

 It looks like the clang assembler has crashed somewhere around line `build
 8` or `build 9` in `libLLVM.dylib` asmParser.

 building compilers is very challenging on the toolchain.

 my first thought would be to try to disable the `clang-7.0` dependency in
 the `gcc` Portfile and then deactivate `clang-7.0` and try again. That
 should make `as` use the system clang, which should work.

 And it has crossed my mind that maybe we're being a bit nutty to even have
 a `cctools` port and an `ld64` port on these very new systems -- sometimes
 these ports seem to cause nothing but trouble for no visible benefit. Just
 having an empty port (like libcxx is on newer systems) would be a lot
 simpler than all our shenanigans.

-- 
Ticket URL: <https://trac.macports.org/ticket/58442#comment:2>
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