[MacPorts] #54949: gcc5 @5.4.0_2 fails to build on macOS 10.13

[MacPorts]

#54949: gcc5 @5.4.0_2 fails to build on macOS 10.13
-------------------------+------------------------
  Reporter:  matteopuel  |      Owner:
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:
Resolution:              |   Keywords:  highsierra
      Port:  gcc5        |
-------------------------+------------------------

Comment (by kencu):

 Having said all that, this seems to be homebrew's one and only
 patch[https://github.com/Homebrew/homebrew-
 core/pull/17569/commits/2cff2c2c1f80c56b6eda1e5137a92a5a6493c565], which
 seems far less impressive that the one in gcc's bug report. Would you care
 to give this a try? Looks like it would take 10 seconds to do:

 {{{
 diff -pur a/gcc/system.h b/gcc/system.h
 --- a/gcc/system.h      2015-01-05 13:33:28.000000000 +0100
 +++ b/gcc/system.h      2017-09-03 18:28:15.000000000 +0200
 @@ -216,6 +216,7 @@ extern int errno;

  #ifdef __cplusplus
  # include <algorithm>
 +# include <map>
  # include <cstring>
  # include <utility>
  #endif
 }}}

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Ticket URL: <https://trac.macports.org/ticket/54949#comment:7>
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