Use g++ -E as the C++ preprocessor

The problem with gnat46 not building was because gnatboot replaces the stdenv
gcc with the gnat45 gcc, so calling g++ directly as the C++ preprocessor fixes
this.

svn path=/nixpkgs/trunk/; revision=26671

pkgs/development/compilers/gcc-4.6/builder.sh

@@ -8,9 +8,7 @@ mkdir $NIX_FIXINC_DUMMY
 # libstdc++ needs this; otherwise it will use /lib/cpp, which is a Bad
 # Thing.
 export CPP="gcc -E"
-if test "$langCC" = "1"; then
-  export CXXCPP="gcc -E" #We only want this if C++ is enabled
-fi
+export CXXCPP="g++ -E"
 
 if test "$staticCompiler" = "1"; then
     EXTRA_LDFLAGS="-static"

pkgs/development/compilers/gcc-4.6/default.nix

@@ -200,7 +200,7 @@ stdenv.mkDerivation ({
     else null;
 
   inherit noSysDirs profiledCompiler staticCompiler langJava crossStageStatic
-    libcCross crossMingw langCC;
+    libcCross crossMingw;
 
   buildNativeInputs = [ texinfo which ]
     ++ optional (perl != null) perl;