Remove xz

Upstream repo is taken down, there are no trustworthy sources.
Sadly, it got to go for now.

scripts.d/25-xz.sh

@@ -1,41 +0,0 @@
-#!/bin/bash
-
-SCRIPT_REPO="https://github.com/tukaani-project/xz.git"
-SCRIPT_COMMIT="6e8732c5a317a349986a4078718f1d95b67072c5"
-
-ffbuild_enabled() {
-    return 0
-}
-
-ffbuild_dockerbuild() {
-    ./autogen.sh --no-po4a --no-doxygen
-
-    local myconf=(
-        --prefix="$FFBUILD_PREFIX"
-        --disable-symbol-versions
-        --disable-shared
-        --enable-static
-        --with-pic
-    )
-
-    if [[ $TARGET == win* || $TARGET == linux* ]]; then
-        myconf+=(
-            --host="$FFBUILD_TOOLCHAIN"
-        )
-    else
-        echo "Unknown target"
-        return -1
-    fi
-
-    ./configure "${myconf[@]}"
-    make -j$(nproc)
-    make install
-}
-
-ffbuild_configure() {
-    echo --enable-lzma
-}
-
-ffbuild_unconfigure() {
-    echo --disable-lzma
-}