factor grpc extension out to ext-grpc, keep library for now, even though unused

config/ext.json

@@ -232,7 +232,7 @@
             "BSD": "wip"
         },
         "type": "external",
-        "source": "grpc",
+        "source": "ext-grpc",
         "arg-type-unix": "enable-path",
         "cpp-extension": true,
         "lib-depends": [

config/source.json

@@ -151,6 +151,18 @@
             "path": "LICENSE"
         }
     },
+    "ext-grpc": {
+        "type": "url",
+        "url": "https://pecl.php.net/get/grpc",
+        "path": "php-src/ext/grpc",
+        "filename": "grpc.tgz",
+        "license": {
+            "type": "file",
+            "path": [
+                "LICENSE"
+            ]
+        }
+    },
     "ext-imagick": {
         "type": "url",
         "url": "https://pecl.php.net/get/imagick",

src/SPC/builder/extension/grpc.php

@@ -21,15 +21,6 @@ class grpc extends Extension
         if ($this->builder instanceof WindowsBuilder) {
             throw new ValidationException('grpc extension does not support windows yet');
         }
-        if (file_exists(SOURCE_PATH . '/php-src/ext/grpc')) {
-            return false;
-        }
-        // soft link to the grpc source code
-        if (is_dir($this->source_dir . '/src/php/ext/grpc')) {
-            shell()->exec('ln -s ' . $this->source_dir . '/src/php/ext/grpc ' . SOURCE_PATH . '/php-src/ext/grpc');
-        } else {
-            throw new ValidationException('Cannot find grpc source code in ' . $this->source_dir . '/src/php/ext/grpc');
-        }
         if (SPCTarget::getTargetOS() === 'Darwin') {
             FileSystem::replaceFileRegex(
                 SOURCE_PATH . '/php-src/ext/grpc/config.m4',