buildGoPackage: Dont copy sources to $out

Some sources are quite large and they don't seem to offer much value

pkgs/development/go-modules/generic/default.nix

@@ -176,15 +176,6 @@ go.stdenv.mkDerivation (
   installPhase = args.installPhase or ''
     runHook preInstall
 
-    mkdir -p $out
-    pushd "$NIX_BUILD_TOP/go"
-    while read f; do
-      echo "$f" | grep -q '^./\(src\|pkg/[^/]*\)/${goPackagePath}' || continue
-      mkdir -p "$(dirname "$out/share/go/$f")"
-      cp "$NIX_BUILD_TOP/go/$f" "$out/share/go/$f"
-    done < <(find . -type f)
-    popd
-
     mkdir -p $bin
     dir="$NIX_BUILD_TOP/go/bin"
     [ -e "$dir" ] && cp -r $dir $bin