VirtualBox: Fix ALSA audio.

Use a sed replacement to ensure that dynamic loading of libasound works.

pkgs/applications/virtualization/virtualbox/default.nix

@@ -76,6 +76,7 @@ in stdenv.mkDerivation {
     ls kBuild/bin/linux.x86/k* tools/linux.x86/bin/* | xargs -n 1 patchelf --set-interpreter ${stdenv.glibc}/lib/ld-linux.so.2
     ls kBuild/bin/linux.amd64/k* tools/linux.amd64/bin/* | xargs -n 1 patchelf --set-interpreter ${stdenv.glibc}/lib/ld-linux-x86-64.so.2
     find . -type f | xargs sed 's/depmod -a/true/' -i
+    sed -e 's@"libasound.so.2"@"${alsaLib}/lib/libasound.so.2"@g' -i src/VBox/Main/xml/Settings.cpp src/VBox/Devices/Audio/alsa_stubs.c
     export USER=nix
     set +x
   '';