Workaround an issue with the file 5.40 update that prevents makepkg from extracting secondary source tarballs

Fixes https://github.com/Frogging-Family/linux-tkg/issues/215

linux-tkg-config/prepare

@@ -346,6 +346,9 @@ _tkg_srcprep() {
     # add upstream patch
     if [ "$_sub" != "0" ]; then
       msg2 "Patching from $_basekernel to $pkgver"
+      if [ ! -e "$srcdir/patch-${pkgver}" ]; then
+        ( cd "$_where" && xz -dk patch-${pkgver}.xz && mv "$_where"/patch-${pkgver} "$srcdir"/ )
+      fi
       tkgpatch="$srcdir/patch-${pkgver}" && _tkg_patcher
     fi