gentoo-overlay/dev-lang/ghc/files/ghc-8.8.1-revert-CPP.patch

Don't pass CPP options. Otherwise ghc-8.8.1 can't build itself.
Eventually ghc will fix it's headers at propagate defines.

https://gitlab.haskell.org/ghc/ghc/commit/cfd3e0f1cfd16c8f35cae139d2a871a32eb4d2e1
https://gitlab.haskell.org/ghc/ghc/issues/17146

--- a/compiler/main/DriverPipeline.hs
+++ b/compiler/main/DriverPipeline.hs
@@ -1190,6 +1190,9 @@ runPhase (RealPhase Cmm) input_fn dflags
 -----------------------------------------------------------------------------
 -- Cc phase
 
+-- we don't support preprocessing .c files (with -E) now.  Doing so introduces
+-- way too many hacks, and I can't say I've ever used it anyway.
+
 runPhase (RealPhase cc_phase) input_fn dflags
    | any (cc_phase `eqPhase`) [Cc, Ccxx, HCc, Cobjc, Cobjcxx]
    = do
@@ -1211,16 +1214,6 @@ runPhase (RealPhase cc_phase) input_fn dflags
               (includePathsQuote cmdline_include_paths)
         let include_paths = include_paths_quote ++ include_paths_global
 
-        -- pass -D or -optP to preprocessor when compiling foreign C files
-        -- (#16737). Doing it in this way is simpler and also enable the C
-        -- compiler to performs preprocessing and parsing in a single pass,
-        -- but it may introduce inconsistency if a different pgm_P is specified.
-        let more_preprocessor_opts = concat
-              [ ["-Xpreprocessor", i]
-              | not hcc
-              , i <- getOpts dflags opt_P
-              ]
-
         let gcc_extra_viac_flags = extraGccViaCFlags dflags
         let pic_c_flags = picCCOpts dflags
 
@@ -1230,7 +1223,7 @@ runPhase (RealPhase cc_phase) input_fn dflags
         -- hc code doesn't not #include any header files anyway, so these
         -- options aren't necessary.
         pkg_extra_cc_opts <- liftIO $
-          if hcc
+          if cc_phase `eqPhase` HCc
              then return []
              else getPackageExtraCcOpts dflags pkgs
 
@@ -1312,7 +1305,6 @@ runPhase (RealPhase cc_phase) input_fn dflags
                        ++ [ "-include", ghcVersionH ]
                        ++ framework_paths
                        ++ include_paths
-                       ++ more_preprocessor_opts
                        ++ pkg_extra_cc_opts
                        ))