php8{1-4}Extensions.spx: 0.4.18 -> 0.4.20 (#424860)

pkgs/development/php-packages/spx/default.nix

···
 }:
 
 let
-  version = "0.4.18";
+  version = "0.4.20";
 in
 buildPecl {
   inherit version;
···
     owner = "NoiseByNorthwest";
     repo = "php-spx";
     rev = "v${version}";
-    hash = "sha256-Dcv8ncYPIug7e24mvL1gn0x0CeLNAck8djm/r/yiPe8=";
+    hash = "sha256-2MOl9waWY3zK5NzQ19TJKK8kE7xC4K+e9AwV+wyAHZc=";
   };
 
-  configureFlags = [ "--with-zlib-dir=${zlib.dev}" ];
-
-  preConfigure = ''
-    substituteInPlace Makefile.frag \
-      --replace '$(INSTALL_ROOT)$(prefix)/share/misc/php-spx/assets/web-ui' '${placeholder "out"}/share/misc/php-spx/assets/web-ui'
-  '';
+  configureFlags = [
+    "--with-zlib-dir=${zlib.dev}"
+    "--with-spx-assets-dir=${placeholder "out"}/share/misc/php-spx/assets/"
+  ];
 
   meta = {
     changelog = "https://github.com/NoiseByNorthwest/php-spx/releases/tag/${version}";