Add support for truffleruby+graalvm

* Using ruby-build to avoid duplicating too much logic.

ruby-builder-versions.js

@@ -11,7 +11,7 @@ export function getVersions(platform) {
       "2.6.0", "2.6.1", "2.6.2", "2.6.3", "2.6.4", "2.6.5", "2.6.6", "2.6.7", "2.6.8",
       "2.7.0", "2.7.1", "2.7.2", "2.7.3", "2.7.4",
       "3.0.0-preview1", "3.0.0-preview2", "3.0.0-rc1", "3.0.0", "3.0.1", "3.0.2",
-      "head", "debug",
+      "head", "debug"
     ],
     "jruby": [
       "9.1.17.0",
@@ -23,6 +23,10 @@ export function getVersions(platform) {
       "20.0.0", "20.1.0", "20.2.0", "20.3.0",
       "21.0.0", "21.1.0", "21.2.0", "21.2.0.1",
       "head"
+    ],
+    "truffleruby+graalvm": [
+      "21.2.0",
+      "head"
     ]
   }