[MacPorts] #40656: Use -isystem instead of -I in default configure.cppflags

[MacPorts]

#40656: Use -isystem instead of -I in default configure.cppflags
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  Reporter:  ryandesign   |      Owner:  macports-tickets@…
      Type:  enhancement  |     Status:  reopened
  Priority:  Normal       |  Milestone:  MacPorts Future
 Component:  base         |    Version:  2.2.0
Resolution:               |   Keywords:  haspatch
      Port:               |
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Comment (by mohd-akram):

 Since it hasn't been mentioned here, `compiler.limit_flags yes` can be
 used to disable the default behavior. Perhaps we should consider changing
 the default to that.

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Ticket URL: <https://trac.macports.org/ticket/40656#comment:24>
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