gcc-*: homogenize and cleanup expressions without a rebuild

Looks scary but it is a noop.

pkgs/development/compilers/gcc/6/default.nix

@@ -50,8 +50,6 @@ with builtins;
 
 let version = "6.4.0";
 
-    enableParallelBuilding = true;
-
     inherit (stdenv) buildPlatform hostPlatform targetPlatform;
 
     patches =
@@ -257,8 +255,7 @@ stdenv.mkDerivation ({
   ''
   + stdenv.lib.optionalString (langJava || langGo) ''
     export lib=$out;
-  ''
-  ;
+  '';
 
   dontDisableStatic = true;
 
@@ -380,7 +377,8 @@ stdenv.mkDerivation ({
     ++ optional (zlib != null) zlib
     ++ optional langJava boehmgc
     ++ optionals javaAwtGtk xlibs
-    ++ optionals javaAwtGtk [ gmp mpfr ]));
+    ++ optionals javaAwtGtk [ gmp mpfr ]
+  ));
 
   EXTRA_TARGET_FLAGS = optionals
     (targetPlatform != hostPlatform && libcCross != null)
@@ -401,10 +399,13 @@ stdenv.mkDerivation ({
         "-Wl,-rpath-link,${libcCross.out}/lib"
     ]));
 
-  passthru =
-    { inherit langC langCC langObjC langObjCpp langFortran langGo version; isGNU = true; };
+  passthru = {
+    inherit langC langCC langObjC langObjCpp langFortran langGo version;
+    isGNU = true;
+  };
 
-  inherit enableParallelBuilding enableMultilib;
+  enableParallelBuilding = true;
+  inherit enableMultilib;
 
   inherit (stdenv) is64bit;
 
@@ -428,6 +429,7 @@ stdenv.mkDerivation ({
     platforms =
       stdenv.lib.platforms.linux ++
       stdenv.lib.platforms.freebsd ++
+      stdenv.lib.platforms.illumos ++
       stdenv.lib.platforms.darwin;
   };
 }