T10667 and debug tests are broken on OS X

This is due to the use of -g by this testcase, which apparently the broken on Darwin. The test fails with,

=====> T10667(normal) 2 of 18 [0, 1, 0] 
cd ./codeGen/should_compile &&  "/Users/bgamari/ghc/inplace/test   spaces/ghc-stage2" -c T10667.hs -fforce-recomp -dcore-lint -dcmm-lint -dno-debug-output -no-user-package-db -rtsopts -fno-warn-tabs -fno-warn-missed-specialisations -fno-ghci-history  -g > T10667.comp.stderr 2>&1
Compile failed (status 256) errors were:

/var/folders/4l/06tjh3z978l_b5plmkq08ff80000gq/T/ghc56547_0/ghc_1.s:101:2: error:
     error: unknown directive
            .hword 3
            ^

/var/folders/4l/06tjh3z978l_b5plmkq08ff80000gq/T/ghc56547_0/ghc_1.s:129:2: error:
     error: unknown directive
            .hword 1
            ^

/var/folders/4l/06tjh3z978l_b5plmkq08ff80000gq/T/ghc56547_0/ghc_1.s:131:2: error:
     error: unknown directive
            .hword 13
            ^

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Apparently we should be using .short on Darwin.