Fixes how tests access tmpdir

Author: arcanis

test/es-module/test-esm-package-map.mjs

@@ -100,7 +100,7 @@ describe('ESM: --experimental-package-map', () => {
         '--input-type=module',
         '--eval',
         `import dep from 'dep-a'; console.log(dep);`,
-      ], { cwd: '/tmp' });  // Not in any mapped package
+      ], { cwd: tmpdir.path });  // Not in any mapped package
 
       assert.match(stderr, /ERR_PACKAGE_MAP_EXTERNAL_FILE/);
       assert.notStrictEqual(code, 0, stderr);

test/parallel/test-require-package-map.js

@@ -105,7 +105,7 @@ describe('CJS: --experimental-package-map', { concurrency: !process.env.TEST_PAR
         '-e',
         `require('dep-a');`,
       ], {
-        cwd: '/tmp',
+        cwd: tmpdir.path,
         encoding: 'utf8',
       });