kernel: Enable cross compiling

pkgs/os-specific/linux/kernel/perf.nix

@@ -23,8 +23,8 @@ stdenv.mkDerivation {
   # perf refers both to newt and slang
   # binutils is required for libbfd.
   nativeBuildInputs = [ asciidoc xmlto docbook_xsl docbook_xml_dtd_45 libxslt
-      flex bison libiberty libaudit makeWrapper pkgconfig ];
-  buildInputs = [ elfutils python perl newt slang libunwind binutils zlib ] ++
+      flex bison libiberty libaudit makeWrapper pkgconfig python perl ];
+  buildInputs = [ elfutils newt slang libunwind binutils zlib ] ++
     stdenv.lib.optional withGtk gtk2;
 
   # Note: we don't add elfutils to buildInputs, since it provides a
@@ -40,6 +40,10 @@ stdenv.mkDerivation {
       "-Wno-error=unused-const-variable" "-Wno-error=misleading-indentation"
     ];
 
+  makeFlags = if stdenv.hostPlatform == stdenv.buildPlatform
+    then null
+    else "CROSS_COMPILE=${stdenv.cc.prefix}";
+
   installFlags = "install install-man ASCIIDOC8=1";
 
   preFixup = ''
@@ -47,15 +51,6 @@ stdenv.mkDerivation {
       --prefix PATH : "${binutils}/bin"
   '';
 
-  crossAttrs = {
-    /* I don't want cross-python or cross-perl -
-       I don't know if cross-python even works */
-    propagatedBuildInputs = [ elfutils.crossDrv newt.crossDrv ];
-    makeFlags = "CROSS_COMPILE=${stdenv.cc.targetPrefix}";
-    elfutils = elfutils.crossDrv;
-    inherit (kernel.crossDrv) src patches;
-  };
-
   meta = {
     homepage = https://perf.wiki.kernel.org/;
     description = "Linux tools to profile with performance counters";