[MacPorts] #58898: libcxx bootstrapping needs a method to upgrade to the +emulatedtls variant on 10.6 and less

[MacPorts]

#58898: libcxx bootstrapping needs a method to upgrade to the +emulatedtls variant
on 10.6 and less
---------------------+---------------------------------------
  Reporter:  kencu   |      Owner:  kencu
      Type:  defect  |     Status:  assigned
  Priority:  Normal  |  Milestone:
 Component:  ports   |    Version:
Resolution:          |   Keywords:  snowleopard leopard tiger
      Port:  libcxx  |
---------------------+---------------------------------------

Comment (by kencu):

 I actually can build libcxx/libcxxabi by bootstrapping with gcc8.

 gcc8 automatically builds llvm & clang, and then uses that clang to build
 libcxx/libcxxabi with all the toys enabled.

 but gcc8 still has deps on things that require libc++, in the end, so
 we're no further ahead.

 I am very (very) tempted to just put up my libcxx built system_roots for
 10.6, 10.5, and 10.4, all of which have thread_local enabled properly in
 them, and have the libcxx port install those binaries. And if I ever get
 to releasing the clang-7.0 for PPC I have been using, I can add the libc++
 for PPC there too.

 I can leave some instructions in the wiki on how people can build their
 own.

-- 
Ticket URL: <https://trac.macports.org/ticket/58898#comment:24>
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