[MacPorts] #63707: clang-13: fix for SnowLeopard

[MacPorts]

#63707: clang-13: fix for SnowLeopard
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  Reporter:  kencu     |      Owner:  (none)
      Type:  defect    |     Status:  new
  Priority:  Normal    |  Milestone:
 Component:  ports     |    Version:
Resolution:            |   Keywords:  snowleopard haspatch
      Port:  clang-13  |
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Comment (by kencu):

 We have not been able to automatically bootstrap from bare metal
 SnowLeopard to a full TLS-supporting libc++ to date.

 It is still a two step process -- install libcxx, install clang-9.0 or so,
 then reinstall libcxx with emulated_tls.

 I had an idea to use a bootstrap self-contrained version of gcc7 or gcc10
 to build clang-something (maybe clang-5.0?)  against libstdc++, which is
 what Ubuntu does, and use that clang as the bootstrap, to build libcxx
 (with emulated TLS) in one go, and then build clang-9.0, etc against that
 libc++. Just never got around to it.

 Another option -- to download and install a prebuilt libc++ with
 emulated_tls enabled, and then use that to bootstrap to a new one that we
 build, was not encouraged when I floated that balloon.

-- 
Ticket URL: <https://trac.macports.org/ticket/63707#comment:6>
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