chromium: Fix building with WineVine components

Before version 54, the WideVine CDM plugin was built unconditionally and
it seems since version 54 this now is dependent upon a GYP/GN flag on
whether to include the CDM shared library or not.

Also, we now use a patch from Gentoo which should hopefully get the CDM
plugin to work properly, at least according to their bugtracker:

https://bugs.gentoo.org/show_bug.cgi?id=547630

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

pkgs/applications/networking/browsers/chromium/browser.nix

@@ -18,6 +18,11 @@ mkChromiumDerivation (base: rec {
     cp -vLR "$buildPath/locales" "$buildPath/resources" "$libExecPath/"
     cp -v "$buildPath/chrome" "$libExecPath/$packageName"
 
+    if [ -e "$buildPath/libwidevinecdmadapter.so" ]; then
+      cp -v "$buildPath/libwidevinecdmadapter.so" \
+            "$libExecPath/libwidevinecdmadapter.so"
+    fi
+
     mkdir -p "$sandbox/bin"
     cp -v "$buildPath/chrome_sandbox" "$sandbox/bin/${sandboxExecutableName}"