[GHC] #13444: Disable diagnostic coloring by default

[GHC]

#13444: Disable diagnostic coloring by default
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        Reporter:  hvr               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  error/warning at compile-time      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by hvr):

 Quoting also https://gcc.gnu.org/gcc-4.9/changes.html when this was
 introduced to GCC:

 > Support for colorizing diagnostics emitted by GCC has been added. The
 `-fdiagnostics-color=auto` will enable it when outputting to terminals,
 `-fdiagnostics-color=always` unconditionally. The `GCC_COLORS` environment
 variable can be used to customize the colors or disable coloring. **If
 `GCC_COLORS` variable is present in the environment, the default is
 `-fdiagnostics-color=auto`, otherwise `-fdiagnostics-color=never`.**

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13444#comment:1>
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