pypy: use the official sitePackages install path

pkgs/development/interpreters/pypy/default.nix

@@ -119,7 +119,7 @@ let
       isPypy = true;
       buildEnv = callPackage ../python/wrapper.nix { python = self; };
       interpreter = "${self}/bin/${executable}";
-      sitePackages = "lib/${libPrefix}/site-packages";
+      sitePackages = "site-packages";
     };
 
     enableParallelBuilding = true;  # almost no parallelization without STM

pkgs/development/interpreters/pypy/setup-hook.sh

@@ -1,12 +1,12 @@
 addPythonPath() {
-    addToSearchPathWithCustomDelimiter : PYTHONPATH $1/lib/pypy2.6/site-packages
+    addToSearchPathWithCustomDelimiter : PYTHONPATH $1/site-packages
 }
 
 toPythonPath() {
     local paths="$1"
     local result=
     for i in $paths; do
-        p="$i/lib/pypy2.6/site-packages"
+        p="$i/site-packages"
         result="${result}${result:+:}$p"
     done
     echo $result