Migrated remaining tests in devtools/build/lib to JUnit 4.

--
MOS_MIGRATED_REVID=109287267
diff --git a/src/test/java/com/google/devtools/build/lib/unix/FilesystemUtilsTest.java b/src/test/java/com/google/devtools/build/lib/unix/FilesystemUtilsTest.java
index f915304..dafcb1c 100644
--- a/src/test/java/com/google/devtools/build/lib/unix/FilesystemUtilsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/unix/FilesystemUtilsTest.java
@@ -42,7 +42,7 @@
   private Path testFile;
 
   @Before
-  public void setUp() throws Exception {
+  public final void createFileSystem() throws Exception  {
     testFS = new UnixFileSystem();
     workingDir = testFS.getPath(new File(TestUtils.tmpDir()).getCanonicalPath());
     testFile = workingDir.getRelative("test");