[MacPorts] #66926: mold uses wrong flags with GCC, breaks the build

[MacPorts]

#66926: mold uses wrong flags with GCC, breaks the build
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  Reporter:  barracuda156  |      Owner:  crowell
      Type:  defect        |     Status:  assigned
  Priority:  Normal        |  Milestone:
 Component:  ports         |    Version:  2.8.1
Resolution:                |   Keywords:  powerpc, leopard, snowleopard
      Port:  mold          |
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Comment (by barracuda156):

 Okay, those `-mrtm` are an effect of using bundled `tbb`.

 `-DMOLD_USE_SYSTEM_TBB=ON` will solve the problem, once my PR is merged:
 https://github.com/macports/macports-ports/pull/14780

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Ticket URL: <https://trac.macports.org/ticket/66926#comment:1>
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