GHC linking fails due to comma in "#default,static"

[ghost]

Having a dependant haskell library will generate a linker command line that contains
-Wl,-rpath '-Wl,/path/to/buck-out/gen/some-library/some-library#default,static'

This causes the clang linker to interpret 'static' as a separate path and to fail with:
ld: file not found: static

I've fixed this for now by changing the comma to a plus: '#default+static'. Would
it be feasible to change this?

[Coneko]

cc @andrewjcg

According to https://github.com/facebook/buck/blob/master/src/com/facebook/buck/cxx/Linkers.java#L40 we should be using -Wlinker when the argument contains ,, not -Wl.

Can you add instructions on how to repro this?