add xdebug dynamic extension

config/ext.json

@@ -888,13 +888,16 @@
         ]
     },
     "xdebug": {
-        "type": "builtin",
+        "type": "external",
         "support": {
             "Windows": "wip",
             "BSD": "no",
             "Darwin": "no",
-            "Linux": "no"
+            "Linux": "wip"
         },
+        "lib-depends": [
+            "xdebug"
+        ],
         "notes": true
     },
     "xhprof": {

config/lib.json

@@ -738,6 +738,12 @@
             "libiconv"
         ]
     },
+    "xdebug": {
+        "source": "xdebug",
+        "static-libs-unix": [
+            "xdebug.so"
+        ]
+    },
     "xz": {
         "source": "xz",
         "static-libs-unix": [

config/source.json

@@ -895,6 +895,17 @@
             "path": "COPYING"
         }
     },
+    "xdebug": {
+        "type": "ghrel",
+        "repo": "xdebug/xdebug",
+        "match": "Source code",
+        "prefer-stable": true,
+        "provide-pre-built": false,
+        "license": {
+            "type": "file",
+            "path": "LICENSE"
+        }
+    },
     "xhprof": {
         "type": "url",
         "url": "https://pecl.php.net/get/xhprof",