backport more changes from 7.8.3 spec to 7.6.3 spec
    
    - remove the build hack to switch from llvm to llvm34 (#1161049)
    - use rpm internal dependency generator with ghc.attr on F21+
    - fix bash-ism in ghc-doc-index (#1146733)
    - do "quick" build when bootstrapping
    - setup LDFLAGS