[MacPorts] #62995: restore_ports fails during migration to macOS 11.[34] (Big Sur) with "requested variants do not match" and also complains "macOS 11 SDK does not appear to be installed"

[MacPorts]

#62995: restore_ports fails during migration to macOS 11.[34] (Big Sur) with
"requested variants do not match" and also complains "macOS 11 SDK does not
appear to be installed"
-------------------------+--------------------
  Reporter:  MarkCallow  |      Owner:  (none)
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.7.1
Resolution:              |   Keywords:
      Port:              |
-------------------------+--------------------

Comment (by MarkCallow):

 I tried `port clean` with sudo and it worked so possibly the original
 failure was my error. Since 2 months have elapsed, I can't be sure.

 I also reinstalled the command line tools manually and `restore_ports.tcl`
 worked without problems. However the fact that xcode-select said they are
 installed shows there is a bug in the code used by the script to check for
 their presence. Manual installation should not have been necessary.

 This whole migration business every time there is a new major macOS
 release is a huge pain. At the very least the process should be fully
 automated, e.g. `sudo port migrate`.

 Thanks for your help Ryan.

-- 
Ticket URL: <https://trac.macports.org/ticket/62995#comment:2>
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