pkg/57090: libcxxabi build failure

[prlw1%cam.ac.uk@localhost]

>Number:         57090
>Category:       pkg
>Synopsis:       libcxxabi build failure
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Nov 24 23:00:01 +0000 2022
>Originator:     Patrick Welche
>Release:        pkgsrc current of 24 Nov 2022
>Organization:
>Environment:
NetBSD-9.99.106/amd64 of 24 Nov 2022
>Description:
Trying to build libcxxabi reproducibly fails with

/tmp/pkgsrc/lang/libcxxabi/work.x86_64/libcxxabi-15.0.5.src/src/cxa_demangle.cpp
:410:1: internal compiler error: Segmentation fault                             
  410 | }  // __cxxabiv1                                                        
      | ^                                                                       
no stack trace because unwind library not available                             
Please submit a full bug report,                                                

using gcc 10.4.0 in base. This is the first time I try building the newish clang 15 version.

I see that I am not alone in seeing the failure:

http://www.ki.nu/pkgsrc/reports/current/NetBSD-9.0/20221122.0018/libcxxabi-15.0.5/build.log
>How-To-Repeat:

>Fix: