[MacPorts] #63118: `llvm-12` build failure in macOS Big Sur 11.4

[MacPorts]

#63118: `llvm-12` build failure in macOS Big Sur 11.4
-------------------------+---------------------
 Reporter:  zhiyuanzhai  |      Owner:  (none)
     Type:  defect       |     Status:  new
 Priority:  Normal       |  Milestone:
Component:  ports        |    Version:  2.7.1
 Keywords:  bigsur       |       Port:  llvm-12
-------------------------+---------------------


-- 
Ticket URL: <https://trac.macports.org/ticket/63118>
MacPorts <https://www.macports.org/>
Ports system for macOS