Adds extra-library-flavours

Not absolutely happy with this solution. I fail to come up with a better one though.
The issue is that for some libraries, you might want to have _debug, _p, _l, as well as _thr_debug, _thr_p, _thr_l flavours.

Author: angerman

Cabal/Distribution/PackageDescription/FieldGrammar.hs

@@ -385,6 +385,7 @@ buildInfoFieldGrammar = BuildInfo
     <*> monoidalFieldAla "extra-libraries"      (alaList' VCat Token)         L.extraLibs
     <*> monoidalFieldAla "extra-ghci-libraries" (alaList' VCat Token)         L.extraGHCiLibs
     <*> monoidalFieldAla "extra-bundled-libraries" (alaList' VCat Token)      L.extraBundledLibs
+    <*> monoidalFieldAla "extra-library-flavours" (alaList' VCat Token)       L.extraLibFlavours
     <*> monoidalFieldAla "extra-lib-dirs"       (alaList' FSep FilePathNT)    L.extraLibDirs
     <*> monoidalFieldAla "include-dirs"         (alaList' FSep FilePathNT)    L.includeDirs
     <*> monoidalFieldAla "includes"             (alaList' FSep FilePathNT)    L.includes

Cabal/Distribution/PackageDescription/Parse.hs

@@ -502,6 +502,9 @@ binfoFieldDescrs =
  , listFieldWithSep vcat "extra-bundled-libraries"
            showToken          parseTokenQ
            extraBundledLibs   (\xs binfo -> binfo{extraBundledLibs=xs})
+ , listFieldWithSep vcat "extra-library-flavours"
+           showToken          parseTokenQ
+           extraLibFlavours   (\xs binfo -> binfo{extraLibFlavours=xs})
  , listField   "extra-lib-dirs"
            showFilePath       parseFilePathQ
            extraLibDirs       (\xs    binfo -> binfo{extraLibDirs=xs})

Cabal/Distribution/Simple/GHC.hs

@@ -1707,9 +1707,10 @@ installLib verbosity lbi targetDir dynlibTargetDir _builtDir _pkg lib clbi = do
   -- copy the built library files over:
   whenHasCode $ do
     whenVanilla $ do
-      installOrdinary builtDir targetDir       vanillaLibName
-      sequence_ [ installOrdinary builtDir targetDir       l
-                | l <- mkGenericStaticLibName <$> (extraBundledLibs (libBuildInfo lib))]
+      sequence_ [ installOrdinary builtDir targetDir       (mkGenericStaticLibName (l ++ f))
+                | l <- getHSLibraryName (componentUnitId clbi):(extraBundledLibs (libBuildInfo lib))
+                , f <- "":extraLibFlavours (libBuildInfo lib)
+                ]
     whenProf    $ installOrdinary builtDir targetDir       profileLibName
     whenGHCi    $ installOrdinary builtDir targetDir       ghciLibName
     whenShared  $ installShared   builtDir dynlibTargetDir sharedLibName
@@ -1739,7 +1740,6 @@ installLib verbosity lbi targetDir dynlibTargetDir _builtDir _pkg lib clbi = do
 
     compiler_id = compilerId (compiler lbi)
     uid = componentUnitId clbi
-    vanillaLibName = mkLibName              uid
     profileLibName = mkProfLibName          uid
     ghciLibName    = Internal.mkGHCiLibName uid
     sharedLibName  = (mkSharedLibName compiler_id) uid

Cabal/Distribution/Types/BuildInfo.hs

@@ -83,6 +83,10 @@ data BuildInfo = BuildInfo {
                                        --              logic on how this library is built will have to be encoded in a
                                        --              custom Setup for now.  Oherwise cabal would need to lear how to
                                        --              call arbitary lirbary builders.
+        extraLibFlavours  :: [String], -- ^ Hidden Flag.  This set of strings, will be appended to all lirbaries when
+                                       --   copying. E.g. [libHS<name>_<flavour> | flavour <- extraLibFlavours]. This
+                                       --   should only be needed in very specific cases, e.g. the `rts` package, where
+                                       --   there are multiple copies of slightly differently built libs.
         extraLibDirs      :: [String],
         includeDirs       :: [FilePath], -- ^directories to find .h files
         includes          :: [FilePath], -- ^ The .h files to be found in includeDirs
@@ -131,6 +135,7 @@ instance Monoid BuildInfo where
     extraLibs           = [],
     extraGHCiLibs       = [],
     extraBundledLibs    = [],
+    extraLibFlavours    = [],
     extraLibDirs        = [],
     includeDirs         = [],
     includes            = [],
@@ -175,6 +180,7 @@ instance Semigroup BuildInfo where
     extraLibs           = combine    extraLibs,
     extraGHCiLibs       = combine    extraGHCiLibs,
     extraBundledLibs    = combine    extraBundledLibs,
+    extraLibFlavours    = combine    extraLibFlavours,
     extraLibDirs        = combineNub extraLibDirs,
     includeDirs         = combineNub includeDirs,
     includes            = combineNub includes,

Cabal/Distribution/Types/BuildInfo/Lens.hs

@@ -135,6 +135,10 @@ class HasBuildInfo a where
    extraBundledLibs = buildInfo . extraBundledLibs
    {-# INLINE extraBundledLibs #-}
 
+   extraLibFlavours :: Lens' a [String]
+   extraLibFlavours = buildInfo . extraLibFlavours
+   {-# INLINE extraLibFlavours #-}
+
    extraLibDirs :: Lens' a [String]
    extraLibDirs = buildInfo . extraLibDirs
    {-# INLINE extraLibDirs #-}
@@ -268,6 +272,9 @@ instance HasBuildInfo BuildInfo where
     extraBundledLibs f s = fmap (\x -> s { T.extraBundledLibs = x }) (f (T.extraBundledLibs s))
     {-# INLINE extraBundledLibs #-}
 
+    extraLibFlavours f s = fmap (\x -> s { T.extraLibFlavours = x }) (f (T.extraLibFlavours s))
+    {-# INLINE extraLibFlavours #-}
+
     extraLibDirs f s = fmap (\x -> s { T.extraLibDirs = x }) (f (T.extraLibDirs s))
     {-# INLINE extraLibDirs #-}