Fix swc test path from node_modules (#66047)

Noticed while testing turbopack version of tests that we weren't loading
the correct swc binary since this path wasn't absolute and was just the
relative path in `node_modules`.

---------

Co-authored-by: Zack Tanner <1939140+ztanner@users.noreply.github.com>

test/lib/create-next-install.js

@@ -100,9 +100,18 @@ async function createNextInstall({
           const swcDirectory = fs
             .readdirSync(path.join(origRepoDir, 'node_modules/@next'))
             .find((directory) => directory.startsWith('swc-'))
-          process.env.NEXT_TEST_NATIVE_DIR = swcDirectory
+          process.env.NEXT_TEST_NATIVE_DIR = path.join(
+            origRepoDir,
+            'node_modules/@next',
+            swcDirectory
+          )
         }
 
+        // log for clarity of which version we're using
+        require('console').log({
+          swcDirectory: process.env.NEXT_TEST_NATIVE_DIR,
+        })
+
         pkgPaths = await rootSpan
           .traceChild('linkPackages')
           .traceAsyncFn((span) =>