How/where to add global ghc flags

[timmytofu]

EDITED:

I have g:ghcmod_ghc_options set to "-fno-warn-unused-binds" but I'm still getting "Defined but not used" warnings.

Running :echo ghcmod#build_command(["check"]) the output I get is

['ghc-mod', '-g', '-i/home/username/path/dist/build/autogen', '-g', '-I/home/username/path/dist/build/autogen',
'-g', '-optP-include', '-g', '-optP/home/username/path/dist/build/autogen/cabal_macros.h', '-g', '-i/home/username/path/dist/build/criterion/criterion-tmp',
'-g', '-I/home/username/path/dist/build/criterion/criterion-tmp', '-g', '-i/home/username/path/dist/build/doctest/doctest-tmp',
'-g', '-I/home/username/path/dist/build/doctest/doctest-tmp', '-g', '-i/home/username/path/dist/build/hlint/hlint-tmp',
'-g', '-I/home/username/path/dist/build/hlint/hlint-tmp', '-g', '-i/home/username/path/dist/build/hspec/hspec-tmp',
'-g', '-I/home/username/path/dist/build/hspec/hspec-tmp', '-g', '-i/home/username/path/dist/build/route-test/route-test-tmp',
'-g', '-I/home/username/path/dist/build/route-test/route-test-tmp', '-g', '-i/home/username/path/dist/build/project/project-tmp',
'-g', '-I/home/username/path/dist/build/project/project-tmp', '-g', '-fno-warn-unused-binds', 'check']

so it's in there, and if I run that very command at the shell, those warnings are supressed. So, the only conclusion I can come up with is that ghcmod-vim does not actually call build_command, or calls it at a strange time such that that global variable is unset and it hangs on to the build command, or plays with it afterwards.