[MacPorts] #54900: libgcc - Build failure with macOS 10.13

[MacPorts]

#54900: libgcc - Build failure with macOS 10.13
--------------------------+--------------------
 Reporter:  cjones051073  |      Owner:
     Type:  defect        |     Status:  new
 Priority:  Normal        |  Milestone:
Component:  ports         |    Version:  2.4.1
 Keywords:                |       Port:  libgcc
--------------------------+--------------------
 Running newly release macOS 10.13. Xcode and CLI tools fully updated.

 building libgcc gives

 {{{
 :info:build                  from
 /opt/local/var/macports/build/_Users_chris_Projects_MacPorts_ports_lang_gcc7/libgcc/work/gcc-7.2.0/libstdc++-v3/include/precompiled/stdc++.h:110:
 :info:build
 /opt/local/var/macports/build/_Users_chris_Projects_MacPorts_ports_lang_gcc7/libgcc/work/build/x86_64
 -apple-darwin17/libstdc++-v3/include/bits/regex_scanner.h:272:10: fatal
 error: bits/regex_scanner.tcc: No such file or directory
 :info:build  #include <bits/regex_scanner.tcc>
 }}}

 Full log attached.

 Port has no maintainer, so not sure who to cc. Looks similar though to

 https://trac.macports.org/ticket/54829

--
Ticket URL: <https://trac.macports.org/ticket/54900>
MacPorts <https://www.macports.org/>
Ports system for macOS