Force top-level graceful-fs to be 4.2.4, and add a sanity test

(This makes sure all the graceful-fs'es dedupe to the right
version so there's only one copy of the cached cwd while
jest executes)

package.json

@@ -21,6 +21,7 @@
     "jsii-rosetta": "^1.4.1",
     "lerna": "^3.20.2",
     "standard-version": "^7.1.0",
+    "graceful-fs": "^4.2.4",
     "typescript": "~3.8.3"
   },
   "repository": {

packages/decdk/test/sanity.test.ts

@@ -0,0 +1,15 @@
+import * as path from 'path';
+
+test('path.resolve is sane', async () => {
+  // Reasons why this might not be true:
+  // graceful-fs, which is used by Jest, hooks into process.cwd() and
+  // process.chdir() and caches the values. Because... profit?
+
+  const targetDir = path.join(__dirname, 'fixture');
+
+  process.chdir(targetDir);
+  expect(process.cwd()).toEqual(targetDir);
+
+  const resolved = path.resolve('.');
+  expect(resolved).toEqual(targetDir);
+});