[MacPorts] #43762: Update arb to 6.0-rc2

[MacPorts]

#43762: Update arb to 6.0-rc2
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  Reporter:  matt.cottrell@…  |      Owner:  macports-tickets@…
      Type:  update           |     Status:  new
  Priority:  Normal           |  Milestone:
 Component:  ports            |    Version:  2.2.1
Resolution:                   |   Keywords:  haspatch maintainer
      Port:  arb              |
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Comment (by mf2k@…):

 I tried to blacklist Macports gcc but it did not seem to help:

 {{{
 compiler.blacklist *llvm-gcc-4.2 macports-gcc-*
 }}}

 Please review UsingTheRightCompiler.

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Ticket URL: <https://trac.macports.org/ticket/43762#comment:8>
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