cc-wrapper: Set CC/CXX more specifically if possible

pkgs/build-support/cc-wrapper/default.nix

@@ -160,12 +160,18 @@ stdenv.mkDerivation {
         wrap ld.bfd ${./ld-wrapper.sh} $binutils/bin/ld.bfd
       fi
 
+      export real_cc=cc
+      export real_cxx=c++
       if [ -e $ccPath/gcc ]; then
         wrap gcc ${./cc-wrapper.sh} $ccPath/gcc
         ln -s gcc $out/bin/cc
+        export real_cc=gcc
+        export real_cxx=g++
       elif [ -e $ccPath/clang ]; then
         wrap clang ${./cc-wrapper.sh} $ccPath/clang
         ln -s clang $out/bin/cc
+        export real_cc=clang
+        export real_cxx=clang++
       fi
 
       if [ -e $ccPath/g++ ]; then

pkgs/build-support/cc-wrapper/setup-hook.sh

@@ -34,5 +34,5 @@ if [ -n "@coreutils@" ]; then
     addToSearchPath PATH @coreutils@/bin
 fi
 
-export CC=cc
-export CXX=c++
+export CC=@real_cc@
+export CXX=@real_cxx@