8.4 download imap separately, compatible with 8.1-8.3

config/ext.json

@@ -255,7 +255,8 @@
             "BSD": "wip"
         },
         "notes": true,
-        "type": "builtin",
+        "type": "external",
+        "source": "ext-imap",
         "arg-type": "custom",
         "lib-depends": [
             "imap"

config/source.json

@@ -259,6 +259,18 @@
             "path": "LICENSE"
         }
     },
+    "ext-imap": {
+        "type": "url",
+        "url": "https://pecl.php.net/get/imap",
+        "path": "php-src/ext/imap",
+        "filename": "imap.tgz",
+        "license": {
+            "type": "file",
+            "path": [
+                "LICENSE"
+            ]
+        }
+    },
     "inotify": {
         "type": "url",
         "url": "https://pecl.php.net/get/inotify",