[GHC] #11684: Fix tests with Clang

[GHC]

#11684: Fix tests with Clang
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        Reporter:  erikd             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by erikd):

 My change modifies `FPTOOLS_SET_C_LD_FLAGS` from `aclocal.m4` as follows:

 {{{
 diff --git a/aclocal.m4 b/aclocal.m4
 index 49c575e..de24752 100644
 --- a/aclocal.m4
 +++ b/aclocal.m4
 @@ -615,6 +615,10 @@ AC_DEFUN([FPTOOLS_SET_C_LD_FLAGS],
      then
          $2="$$2 -fno-stack-protector"
      fi
 +    if $CC -c conftest.c -Qunused-arguments > /dev/null 2>&1
 +    then
 +        $2="$$2 -Qunused-arguments"
 +    fi
 }}}

 If that modifies the CFLAGS for the stage0 compiler then this is obviously
 the wrong approach.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11684#comment:3>
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