build-support/php: move environment variables under `env` attribute

pkgs/build-support/php/build-composer-project.nix

···
         composerStrictValidation = previousAttrs.composerStrictValidation or true;
       };
 
-      COMPOSER_CACHE_DIR = "/dev/null";
-      COMPOSER_DISABLE_NETWORK = "1";
-      COMPOSER_MIRROR_PATH_REPOS = "1";
+      env = {
+        COMPOSER_CACHE_DIR = "/dev/null";
+        COMPOSER_DISABLE_NETWORK = "1";
+        COMPOSER_MIRROR_PATH_REPOS = "1";
+      };
 
       meta = previousAttrs.meta or { } // {
         platforms = lib.platforms.all;

pkgs/build-support/php/build-composer-repository.nix

···
           runHook postInstallCheck
         '';
 
-      COMPOSER_CACHE_DIR = "/dev/null";
-      COMPOSER_MIRROR_PATH_REPOS = "1";
-      COMPOSER_HTACCESS_PROTECT = "0";
-      COMPOSER_DISABLE_NETWORK = "0";
+      env = {
+        COMPOSER_CACHE_DIR = "/dev/null";
+        COMPOSER_MIRROR_PATH_REPOS = "1";
+        COMPOSER_HTACCESS_PROTECT = "0";
+        COMPOSER_DISABLE_NETWORK = "0";
+      };
 
       outputHashMode = "recursive";
       outputHashAlgo =

pkgs/build-support/php/pkgs/composer-local-repo-plugin.nix

···
     hash = "sha256-edbn07r/Uc1g0qOuVBZBs6N1bMN5kIfA1b4FCufdw5M=";
   };
 
-  COMPOSER_CACHE_DIR = "/dev/null";
-  COMPOSER_MIRROR_PATH_REPOS = "1";
-  COMPOSER_HTACCESS_PROTECT = "0";
-  COMPOSER_DISABLE_NETWORK = "1";
+  env = {
+    COMPOSER_CACHE_DIR = "/dev/null";
+    COMPOSER_MIRROR_PATH_REPOS = "1";
+    COMPOSER_HTACCESS_PROTECT = "0";
+    COMPOSER_DISABLE_NETWORK = "1";
+  };
 
   nativeBuildInputs = [ makeBinaryWrapper ];