pkgs/phps: Fix type error

configureFlags should take array but lib.optionalString will return
a string when the condition is false. It only ever worked because
we always run the code on PHP < 7.4 and lib.optionalString returns
the argument as is when the condition is false.

Author: jtojnar

flake.nix

@@ -10,10 +10,15 @@
 
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
 
+    php-src = {
+      url = "github:php/php-src";
+      flake = false;
+    };
+
     utils.url = "github:numtide/flake-utils";
   };
 
-  outputs = { self, flake-compat, nixpkgs, utils }:
+  outputs = { self, flake-compat, nixpkgs, php-src, utils }:
     # For each supported platform,
     utils.lib.eachDefaultSystem (system:
       let
@@ -29,14 +34,16 @@
         };
       in rec {
         packages = {
-          inherit (pkgs) php php56 php70 php71 php72 php73 php74 php80 php81;
+          inherit (pkgs) php php56 php70 php71 php72 php73 php74 php80 php81 php-master;
         };
 
         checks = import ./checks.nix {
           inherit packages pkgs system;
         };
       }
     ) // {
-      overlay = import ./pkgs/phps.nix nixpkgs.outPath;
+      overlay = import ./pkgs/phps.nix {
+        inherit nixpkgs php-src;
+      };
     };
 }

pkgs/phps.nix

@@ -1,4 +1,7 @@
-nixpkgs:
+{
+  nixpkgs,
+  php-src,
+}:
 
 # These are older versions of PHP removed from Nixpkgs.
 
@@ -43,7 +46,7 @@ let
 
           configureFlags =
             attrs.configureFlags
-            ++ prev.lib.optionalString (prev.lib.versionOlder args.version "7.4") [
+            ++ prev.lib.optionals (prev.lib.versionOlder args.version "7.4") [
               # phar extension’s build system expects hash or it will degrade.
               "--enable-hash"
             ];