non-default ghc versions

[srid]

include these other package sets

• include handpicked ghc versions
• upstream MapRoute Add MapRoute ema#144
• nav bar to display ghc versions
• don't hardcode compiler versions list in Nix (fix the evaluation issue)

[srid]

this seems to require building those ghc's

warning: Git tree '/Users/srid/code/NixHaskellIndex' is dirty
error: Package ‘compiler-rt-libc-7.1.0’ in /nix/store/3c1mcvhsxcxmrk9z4z3cn3hg9rbwabla-source/pkgs/development/compilers/llvm/7/compiler-rt/default.nix:100 is marked as broken, refusing to evaluate.